At the title screen, press the following for the desired affect. It must be done quickly and you will get a sound confirmation.

Effect	Code
Allows 5 credits instead of 3 in Options	Hold Down and press C, A, A, B, A, A, C, A, A.
Alternative vehicle colors	Hold Up and press A, C, B, B, A, C, A, C, B.
Level Select (1 to 3) in Options	Hold Left and press B, B, C, A, B, C, B, C, A.