I did find some codes that may help you out. These are all entered on the main menu screen:
Down, Up, Left, Down, Right, Up, Square, Triangle -- castrol cash
Left, Up, Left, Down, Left, Down, Right, Square. -- Infinite Nitrous
Down, Up, Up, Right, Left, Left, Right, Square -- Unlimited Crew Charge
Down, Right, Right, Left, Right, Up, Down, Square -- Unlimited Speedbreaker
Right, Up, Down, Up, Down, Left, Right, Square - Unlocks the NFS:C Vinyl
Up, Up, Down, Down, Down, Down, Up, Square -- Unlocks the cardboard Box and Driver vinyl