When in the Garage, type in the code then click on "fine tune specific parts".

Code	Effect
americanmuscles	MC GTLE in your Garage
bavariancheetah	Balenr GT3 in your Garage
begformoney	$1,000,000
catchmywheels	Furrano GTS in your Garage
dragstarr	'Drag Starr' Hauler's SD750
granturismo	Focer WRC in your Garage
hellofromtokyo	Nonus GT2 in your Garage
iamcoolguy	3000 prestige points and four secret buttons in club info
iloverallies	Enula WRST in your Garage
kickassreddevil	Teleports you to the Red Club and places you 1st in the club rating
primemyride	Prime DLH500 in your Garage
racingforreal	Duhen CDVC in your Garage
xtremetuner	Einvagen 140GTA in your Garage