experiment with your gear ratios, start out by playing with the "Sport----Wide" slider. Sport is more acceleration, which you need from what I understand, and wide is a higher top speed.
If your car is accelerating all the way around the test track, move your slider to sport, a few notches at a time. If you are in 5th out of 6 gears, move your slider to sport. On the other hand, if you are halfway down a long straightaway, and your rev limiter kicks in, move your auto setting toward wide.