Use the following cheat codes:
All Arcade tracks: ALLTRACKSPLEASE
All Arcade cars: ALLTHECARSNOW
All Championship cars: ENDOFFERS
All LeMans cars: LEMANSOFFERS
All Run cars: 1999CHEATCARS
99 BMW LMP in training mode: 19BMW99
99 Audi Roadster in training mode: 1999AUDI
99 Toyota in training mode: TOYOTA1999
Easy racing: MAKEITPEASY
Return to normal racing: MAKEITNORMAL
Deborah in training mode: DEBORACING
Deborah in run mode: DEBORALM