Jason Bos – 2003 Volkswagen Golf GTI
Original Story by Adam Gordon
Updated by PAS Staff
Photography by Russell MacDonald (@basisvisuals)
We’re revisiting Jason Bos’ 2003 Volkswagen Golf GTI — a handmade, widebody, turbocharged show build that blurred the line between feature car and fabrication portfolio. When the GTI first appeared in PASMAG Issue #156, its hand-shaped sheet-metal over-fenders, custom three-piece Enkei RPF1 conversion, Air Lift Performance suspension, and JB MaF-built details made it unlike almost any Golf we had seen before.
Years later, the car itself has largely held its form. That might sound uneventful, but in this case, it says a lot. The GTI remains a snapshot of Bos’ fabrication skill, while JB MAF has continued to grow from after-hours shop work into a full-time operation focused on wheel refinishing equipment, ceramic polishing, redrilling, and surface finishing.
Still Holding Its Shape
According to Bos, the GTI has held up well over the years, spending most of its time in the same garage and personal workshop where much of the original fabrication took place. The handmade sheet-metal over-fenders — shaped with an English wheel, Pullmax, hammer, and dolly — have stood the test of time, even after one major scare.
At one point, a friend backed a Subaru into the driver-side rear quarter, collapsing one of the custom over-fenders. Considering each fender originally took nearly 40 hours to create, it could have been a brutal setback. Instead, Bos pulled the wrap, reshaped the damaged panel with hammer-and-dolly work, skimmed it with body filler, primed and blocked it, and had the car rewrapped in time for that year’s show season. Because the over-fenders had been mounted with rivnuts, removal and installation were straightforward.
The wheel setup has also held its form, though Bos admits the car’s aggressive tire sizing and lack of creature comforts make it more show car than polished driver. With wide front and rear tires, no air conditioning, no power steering, and a base tune still waiting for further refinement, the GTI has a habit of wandering under hard pulls. The Air Lift setup remains useful for airing out when parked or stopping for fuel, but if he were building the car today, Bos says a spring or coilover-based setup might have better suited a more driver-focused version of the car.
The turbo setup has survived as well, partly because the GTI doesn’t log many driving hours. The custom manifold and boost piping remain in place, but the hood-exit setup still delivers the occasional fireball on deceleration — sometimes directly in view of the windshield.
“I usually reach over and touch my extinguisher and mentally prepare for a disaster,” Bos says.
The Craft Still Matters
Looking back, the part of the GTI Bos remains most proud of is still the sheet-metal work. The widebody was not simply a visual modification; it was a learning process rooted in advanced metal-shaping techniques. The fenders required reverse curves, a complex form that involves both stretching and deep shrinking the metal to create the proper shape.
Bos made his own thumbnail dies for the Pullmax to help achieve those deep shrinking operations. Once the first fender shape was developed, each subsequent panel came together more efficiently, but the process remained highly technical.
“Sheet metal is a lot like fabric in the sense where you have to move it to create shapes,” Bos explains.
That relationship between material, process, and final form still runs through his work today. The same problem-solving approach that shaped the GTI’s fenders also appears in the upholstery, wheel refinishing, and equipment-building work that has become part of the JB MAF story.
If He Built It Today
If Bos were building the GTI again today, the direction would be different. Rather than leaning into the full show-car treatment, he says he would likely strip the interior, remove the audio system, skip the diamond-stitched upholstery, and build the car as something closer to a true race car with two seats and a solid paint job.
He also says modern tools would likely change the material direction. With 3D scanning, 3D printing, and his long-running interest in carbon fiber, a current version of the car might trade sheet metal for exposed carbon components — less because the original fenders were heavy, and more because learning a new skill has always been part of the point.
From Garage Craft to JB MAF
JB MAF was already developing in the background when the GTI first became known. Bos traces the early days back to around 2013, when he was selling camber shims on VW Vortex. Around the same period, he purchased his first house with a large shop behind it and began filling the space with milling machines, lathes, welders, fabrication equipment, and metal-shaping tools.
For years, JB MAF existed as an after-hours operation. That changed in September 2021, when Bos purchased his first commercial condo unit and moved into the business full-time. By then, he had finished the second version of his ceramic polishing system, applying lessons learned from the first prototype. Two months after opening JB MAF Inc., the company sold its first machine.
Since then, the business has grown significantly. JB MAF has become recognized for wheel refinishing equipment, ceramic polishing systems, brushing and polishing machines, prep and repair equipment, and related tools used by manufacturers and wheel repair shops. Bos says equipment sales are now heavily focused in the United States, with international growth that includes the Australian market. Seeing JB MAF equipment used by larger operations, including JTX Forged, has helped establish the company further in the wheel manufacturing and refinishing space.
JB MAF has also doubled in physical size through the acquisition of a second commercial unit. One building remains focused on production wheel polishing and wheel redrilling, while the other is dedicated to equipment design, manufacturing, and assembly. The company now handles design, welding, fabrication, painting, wiring, panel building, mechanical assembly, and urethane casting in-house.
“Building a car can be seen in some respects like running a business. Planning, budgets, and scheduling are all part of pulling something off in a timeframe. The only difference is one is a giant money pit and the other one makes you money.”
Current Work: Advan Siena Gen II Refinish
One of the current JB MAF projects Bos documented for this refresh centers around a set of Advan Siena Generation II wheels — a cult-favorite, discontinued JDM multi-piece wheel from the late-’90s and early-2000s Japanese wheel world.
The process began with chemical stripping after the wheels were separated, allowing the faces, lips, and barrels to be processed individually. After a three-stage ceramic polishing process, the faces were mounted on the JBMF-50 brush, polish, and prep workstation to create a brushed front surface finish that complemented the ceramic-polished windows. The high-speed brushing machine spins forward and reverse to create a uniform brushed finish, which was then sealed with a clear finish designed to preserve the visible brush lines rather than bury them under thick powder.
The faded anodized caps were re-anodized to restore their vibrant blue color, while the lips were polished manually on the workstation. Reassembly proved to be one of the most difficult parts of the job because of the barrel’s recessed profile near the nuts, which required a claw-foot wrench and a second person to hold each screw stationary from the front of the wheel.
For Bos, the project stands as one of JB MAF’s favorite wheel refinishing jobs to date — and a clear example of how the same hands-on problem solving that shaped the GTI continues to define the business today.
The Original Feature
View the original PASMAG Issue #156 3D feature experience
Does the GTI before you look unlike any Golf you’ve ever seen before? It should. That’s because very few of the visible parts on this car are available for purchase anywhere. Jason Bos isn’t your average Volkswagen enthusiast. Instead of catalog shopping for parts to improve his 2003 Golf GTI’s driveability, appearance, and overall quality, Bos took it upon himself to put in the hard work himself. Having worked as a machinist and fabricator for nearly two decades, he decided he would learn some new skills to experiment on his own car.
“I've always enjoyed making things, whether it's from fabric, metal, or wood,” Bos tells us, reflecting on his hands-on nature and how it applied to car building. “A car is just a large canvas that lets you try different things.” That big blank canvas was a playground for Bos in the early stages of the build. Bos has owned the car for six years, but its current iteration started about three years into his time with the car, and lasted another three years to reach the point it’s at now. Rome wasn’t built in a day, after all.
One of the most incredible and immediately noticeable features on this build is the super wide widebody kit. No universal ABS plastic fender flares here — the pieces of this kit are all hand-made by Bos himself out of sheet metal, after learning some new skills and making some new tools for his machines to help stretch the material with minimal tooling marks. Bos extends a thank-you to Empire Fabrication, an American fabrication company who gave Bos some advice on the process when he called for some help. Once he had figured out the right way to craft a proper reverse curve in the metal, he was proficient in the process by the time he reached the last one.
With his custom fender flares made, he added a splitter, metal side skirts, and spoiler brackets, all hand-made to match the car’s growing widebody aesthetic. With the GTI now several inches wider on each side, the rest of the car’s components needed to work in tandem with that. Matching the car’s width at the highest level is an APR GT250 carbon fiber spoiler attached to Bos’ custom spoiler brackets, reaching almost as far out as the fenders themselves. From top to bottom the car is full of custom surprises, and at ground level you may notice something extra unique.
If you know your wheels, you’ve probably spent a bit of time examining the very special Enkei RPF1 wheels in a three-piece variation. You might be thinking to yourself that three-piece Enkei RPF1s don’t exist — and until Bos came along, you would have been right. After splitting a set of RPF1s on his lathe, he had lips and barrels sourced by Righteous Garage, and put together the world’s first three-piece set of Enkei RPF1 wheels, complete with 6-inch lips up front, and 7-inch lips in the rear, with the entire assembly held together with gold M7 hardware. Once completed, the custom RPF1s measured 18x11.5 up front, and 18x13 in the rear. Adding the final finishing touch to the custom wheels is a special JB MaF center cap to let people know just who made them.
Allowing the Toyo tires to tuck beneath the wide metal fenders and achieve perfect fitment is a full Air Lift Performance air suspension system, which is managed by a tank, compressor and hardline setup displayed beautifully in the trunk. That trunk setup sits just beneath a green painted, custom fabricated roll cage, and atop a completely reupholstered trunk floor, complete with diamond-pleated leather and a JB MaF CNC-machined logo plate. Flip a switch, and the internal trunk access door opens via air actuation to show off the battery, compressor, and Zapco 1000-watt amplifier that powers his JL Audio 8W7 subwoofers in a custom enclosure. The entire trunk setup was designed and fabricated by Bos himself, making for an incredible show display that he can truly take pride in.
Once the show-worthy nature of the vehicle was well taken care of, Bos directed his attention to ensuring the GTI’s performance matched the aggressive looks. In the three years before he had amassed enough metalworking skills to commit to the car’s transformation, Bos had added a bigger turbo, injectors, and an intercooler around two years into owning the car. Knowing he would eventually want more, he planned ahead, and built the bottom end of his AWP 1.8T with Integrated Engineering connecting rods. He also took this time to install a South Bend stage 2 clutch and a Peloquin LSD.
All of that performance preparation paid off in the summer of 2018. After acquiring and hoarding a handful of parts over the years, it was time to make some power. A Precision 5858 turbocharger would replace his old turbo, and Bos’ fabrication skills would once again come into play as he made his own turbo manifold, intercooler piping, and custom machined Hemi throttle body made to fit on his SEM Motorsport intake manifold. Fuel delivery was taken care of by a Walbro 450 fuel pump and Grams performance 1000cc injectors, and a custom tune from Doman8 brought the entire system into harmony to make a potent 450 estimated wheel horsepower.
Since completing the GTI, Bos has earned numerous prestigious accolades at shows both local and abroad. After building a custom bagged trailer last year to bring the car to far away shows, the urge to drive the car more has been taking hold, and he says he will be doing a lot more of that this year. Ultimately, the build was not only a stellar show piece, but also a great learning experience for Bos to hone his skills. He tells us that his next build will utilize those same skills to create something more performance oriented, and less show-car. Whatever it is, we’re here for it.
Originally featured in PASMAG Issue #156
Click here to order PASMAG Issue #156.
ESSENTIALS
OWNER:
Jason Bos
VEHICLE:
2003 Volkswagen Golf GTI
LOCATION:
Kitchener, ON
ENGINE:
Volkswagen AWP turbocharged 1.8L I4
HORSEPOWER:
450 whp estimated
SOCIAL:
Facebook: jason.bos.129
Instagram: @jb_maf
ENGINE:
Integrated Engineering connecting rods + Precision Turbo 5858 turbocharger and 38mm wastegate + Grams Performance 1000cc injectors + SEM Motorsport intake manifold + TiAL BOV + JB MaF custom turbo manifold, intercooler piping, 3-inch cold-air intake, and machined Hemi throttle body + Vibrant HD clamps + Walbro 450 inline fuel pump + Doman8 custom tune
EXHAUST:
JB MaF custom pie-cut wastegate hood exit
DRIVETRAIN:
Peloquin LSD + South Bend stage 2 clutch
WHEELS / TIRES / BRAKES:
Custom Enkei RPF1 three-piece conversion wheels – 18x11.5 front / 18x13 rear + Toyo Proxes tires – 265/35/18 front / 285/30/18 rear + Custom machined JB MaF center caps and brake adapters + Gold M7 hardware + Mitsubishi CT9A Brembo brake calipers + Stim Technologies hydraulic e-brake
CHASSIS / SUSPENSION:
Air Lift Performance V2 full air suspension system
EXTERIOR:
JB MaF custom metal widebody, front splitter, splitter rods, metal side skirts, hand-shaped fenders, and spoiler bracket + Shaved hood and hatch emblem + Avery Dark Gray Gloss vinyl wrap + APR GT250 carbon-fiber spoiler
INTERIOR:
Custom interior reupholstery + Diamond-pleated headliner, pillars, and trunk setup + Air-actuated trunk access door + JB MaF custom fabricated roll cage and CNC-machined logo trunk display + Sparco Evo Competition driver seat and 4-point harness
AUDIO / MOBILE ELECTRONICS:
Zapco 1000 W old-school amplifier + JL Audio 8W7 subwoofers + Custom subwoofer enclosure
SPONSORS:
Stim Technologies + Toyo Tires + SEM Motorsport + Niko Signs and Grafx + JB MaF
PHOTO CREDIT:
Photography by Russell MacDonald — @basisvisuals
Additional images courtesy of Jason Bos / JB MAF
GALLERY
