To enter the cheat codes select "statistics" option at the main menu, then press Delete or Backspace and go back to the main menu. You can now enter the following codes:
gimmeppablo - Unlock Petey Pablo
gotcharobzombie - Unlock Rob Zombie
allmylvloneparts - Unlock Level 1 Upgrades
allmylvl2parts - Unlock Level 2 Upgrades
gimmesomecircuits - Unlock Circuits
gimmesomesprints - Unlock Sprint Circuits
gimmesomedrag - Unlock Drag Circuits
needmylostprophets - Unlock Lost Prophets
havyamystikal - Unlock Mystikal
119focus - Unlock Car
893neon - Unlock Car
899eclipse - Unlock Car
371impreza - Unlock Car
222lancer - Unlock Car
922sentra - Unlock Car
667tiburon - Unlock Car
334mygolf - Unlock Car
889civic - Unlock Car
228supra - Unlock Car
240240sx - Unlock Car
342integra - Unlock Car
239celica - Unlock Car
973rsx777 - Unlock Car
77peugeot - Unlock Car
777rx7 - Unlock Car
350350z - Unlock Car
111skyline - Unlock Car
221miata - Unlock Car
2000s2000 - Unlock Car