Forza Woes

So I'm still kicking butt in the Professional series but I've hit a snag. In the A class races my Lotus Elise just isn't good enough to catch the Corvette. The problem is accelleration, I can hang with him but just can't get through the gears fast enough to pass him.
So I broke down and bought a Corvette Z06 and added a few parts like racing brakes, and a sports transmission to crank it up a bit but still keep it an A class vehicle. Now I'm able to take the lead but I'm all over the road and sometimes crashing because Corvettes have lousy traction.

I just wish I knew how to tune the Elise because the top players on the leaderboad for theat track are using the same car as me, so how come they can win so easily and I can't even get close? It's got to be the tuning.