If your problem is top speed then just buy full custom trans and set gear ratio to like 13 to 15 at the bottom gear change menu. After doing this it should go from like 153 when u first got it to a good 200 or more with turbocharger, the accelleration wont be harmed 2 much. The car may be a little overpowered and b-spec will end up flying off turns into gravel, to make up for this just increase oversteer. For suspension I just tightened springs 3/4 as far as they go and lowered the car as much as possible which helped with turning ontop of more oversteer.
