Shit, I hate to quote specs, but sometimes you just gotta cut through the bullshit. Here goes:
335i
Unladen 3560 (3582) lbs
Engine: Liter/type/valves per cylinder TwinPower Turbo 3.0/inline 6/4
Nominal output hp/rpm 300/5800
Max. torque lb-ft/rpm 300/1200-5000
Acceleration 0-60 mph (5.5) sec
135i
Unladen weight3373 (3439) lbs
Engine: Liter/type/valves per cylinder TwinPower Turbo 3.0/inline 6/4
Nominal output @ 300hp @ 5800 hp
Maximum torque @ 300 @ 1200-5000 lb-ft
Acceleration 0-60 mph: (5.1) sec 7-SPEED Double Clutch
Stage 1 GTI with intake 0-62mph 5.6sec per APRs numbers
Stage 2 GTI with intake/downpipe 0-60? It's difficult to say as there are no published numbers, but the extra 15-20hp, torque, and wider power band put some estimates I've researched handily btw 5-5.4 with a decent set of tires.
I had 335i too. i know.. i raced with my friend's stage 2 mk6 before the lease return on my 335i. and it was a easy win...
If it was an "easy win" then your friend sucks at driving. Will the beemer win by I hair? I wouldn't be surprised ... but it'll ultimately be a drivers race. A stage 2 GTI will have more torque than the 335. It's lighter (3200lbs) than the 335 and 135, and will be pushing similar hp output (~280 range at stage 2 on 93 octane with an intake and downpipe). Point is, it shouldn't have been an easy win. Period.
so it could be a good race between 135i and stage 3 GTi..
Stage 3 GTI with a decent set of tires would destroy a stock 135i. It would destroy the 335i stock as well. Take a look at the following:
Honestly what it boils down to is RWD vs FWD. Any FWD vehicle will end up hitting a brick wall due to traction issues in the first 2 gears. With as much torque as a tuned GTI puts out (on a FWD car) ... getting power to the ground from a standstill is tricky. Honestly, though, the moral of the story is
who gives a shit about 0-60s. Unless you're an immature adolescent dragging at every other red light, it means nothing.
Passing power, torque, and "usable power" in daily driving and/or around the track are what matter. Once you get past 2nd gear and your wheels aren't spinning, I'd wager that the stage 2 GTI has the pwr/weight ratio to snarf the heavier beemer handily and keep up neck and neck with the lighter beemer (135i) just fine. The pwr/weight ratio on a Stage III kitted GTI is simply insane.