Go to the car selection screen in exhibition mode and highlight Kenny Wallace's car. Then, hold X and press Up, Down.
Increase frame rate
At the options screen, hold Circle and press Up, Left, Down, Right. If you entered the code correctly, a new option that increases the game's frame rate will appear at the bottom of the screen.
Pinnacle Trading Cards car
Go to the car selection screen in exhibition mode and highlight Bobby Labonte's car. Then, hold X and press Up, Down.
Shoot paintballs
Pause the game and display the race statistics screen. Then, hold L1 + R1 + L2 + R2. If you entered the code correctly, you will hear the sound of an engine. Now resume the game and press Triangle to shoot paintballs at other cars.
Waving driver
While driving, select the view in which the driver and steering wheel are visible. Then, hold Triangle until the driver waves.