CPU control
Pause the game, press Select, then unpause the game. Now your car will be controlled by the CPU. Repeat this code to return to normal control.
99,999,900 credits
Go to the "Garage" screen in scenario mode and press Up(2), Down(2), Left, Right, Left, Right, Select.
Full character attributes
Go to the "Garage" screen in scenario mode and press Down(2), Up(2), Right, Left, Right, Left, Select.