Test Dive Off-Road

At the Enter name screen enter these codes:
LOWRIDER = Stock car
FIFTY = Hot Rod
SPRINTER = buggy
FRIENDLY = Track 7
SANDUNE = Speed Demon and Mud Runner Cup
ALLTRACKS = all 12 Tracks

When asked name type one of the following:
CHEAT1 , CHEAT2 , CHEAT3 , CHEAT4, CHEAT5
Just type one at a time and you'll get 4 hidden cars , no cliping , and access to all tracks.