Press L2, L1, R2, R1, X(2), Triangle, Square, Circle to unlock all tracks.
Press Circle, Square, Triangle, X(2), R1, R2, L1, L2 to unlock all cars.
In any race with a countdown, keep the pointer of the tachometer between 4 and 5 to get a good start and a little turbo boost. If you keep it between 5 and 6, you will get a super start and a great turbo boost. If the pointer is in the red (7 and 8) however, you will get an over rev and be stopped for a few seconds while your opponents drive away.
Go to the race type menu and press X on "Racing Line". Then, go to the performance cars and press X on the 1995 GT90 concept car. Then, go to Colonial Run and press X on Harbor Side (the first one). When in the race, as it is counting down slow the RPM gauge between 4000 rpm and 6000 rpm and you will get a boost when it says "Go".