im still having trouble

i got the GT-R working thanks! My Stealth cars were working when i did the hack, i turned my ps3 off to do something else and when i came back on and loaded up GT5 i had a yellow simple with an exclamation mark next to all my stealth cars and chrome line cars, i clicked on one of the cars and says in red writing at the bottom "GTR GT500 Stealth Model is not installed. Please reinstall it" how to i stop this from happening? i cant use the cars because i havnt installed the dlc so do i have to have the dlc to keep them?