Enter one of the following codes at the bonus screen: 


XKIMCF or LEZEJD - unlock all cars 
QTRIKX or TMYTKO - unlock all tracks 
IHHBIV or OATRYU - no damage 
SIM - realistic handling 
DAMAGE - realistic damage 
CREDITS - view credits

At the main screen, type in the following code.

Effect - Cheat
To get a blow-off valve -  markskaife