Jettas came stock with a VR6 from 94-current, so it wouldn't be a VR6 swap. Exactly how fast is your car, then I might be able to tell you what is done to that jetta. My GTI (VR6) only has a chip and intake and will do about 150, so it wouldn't take much for that jetta to do 155, just depends on how fast he got there, cause it runs out of gear at 160.