Unlockable Car Parts
     From  the  main  menu,  select "Extras", then "Cheats". Enter the 
code  and select the checkmark. A message will appear telling you that 
a  new  car  part  has been unlocked. Go to "Story Mode" and enter the 
garage to eqip your new car part.

36mj5v:  Unlocks Hoistein (Hood Ornament)

k4c2sn:  Unlocks Mega Spoiler (Rear Accessory) 

36MJ5VT: Butterfly wheels