Type them at the frontend of the Game or pause the race and type in the cheats.
MACHTHREE - a new car with max speed of 600 km/h (in every race u select).
IMPACT - unlimited ammo in deathmatch.
OVERKILL - weaponmode in championship.
ALLOFF - cheats off.
Enter in the game or in pausemode BUGGYBOY ...
Now you are in Debugmode following codes are in:
A - Autopilot youre car drives allone (besttimes)
F - Displays Framerates
G - Switch between the cars (be sure that you have pressed A before)
I - Informations system ( how wave is active ...and so on)
P - Sreenshoot