At the 'Main' menu select 'Extras' and go to 'Cheats'. Then enter 'z74hsv' (without the quotes) and select the checkmark. If you have entered the code correctly a confirmation message will appear on screen and when you next go to the garage in Story mode you will be able to equip the Butterflies wheels.
At the 'Main' menu go to 'Extras' and then select 'Cheats' and enter the code and select the checkmark. When the new car part has been unlocked you will receive a confirmation message. Then go to 'Story' mode and enter the garage to equip your new car part.
Unlock Hoistein (Hood Ornament): Enter the code 36mj5v
Unlock Mega Spoiler (Rear Accessory): Enter the code k4c2sn