Cheat codes
Pause the game and enter the following button combinations for the corresponding cheat function. You should hear a sound when you press the combinations correctly:

Invisibility -- press R1, L1 (2), R2, L1 (2), L2
Lighter cars -- press L1, R1 (2), L2, R2 (2)
No gravity -- press R1, R2, R1, R2, up (3)
Increase time warp -- press R1, L1, L2, R2, right (3)
Decrease time warp -- press R2, L2, L1, R1, left (3)