Heres all I have:
Porsche Cayman S in demo
Porsche Cayman S unlock in most wanted demo. Enter cheat at start menu.
L1, R1, R1, R1, Right, Left, Right, Down unlocks Porsche Cayman S
Enter at title screen
You will be able to use in the Backroom of the One Stop Shop
up,up,down,down,left,right,up,down unlock a marker
Start Screen Unlocks
Enter at the start screen.
Left, Right, Left, Right, Up, Down, Up, Down Unlocks Castrol SYNTEC Ford GT
Up, Down, Up, Down, Left, Right, Left, Right Unlocks Burger King Challenge
Up, Up, Down, Down, Left, Right, Up, Down Unlocks an Extra Marker for use in shop.