true, yeah thats not it. I remember there being a few ford gts in the game, see if you have the right one.Strife88

I have the "GT40 MK 1"

there should be another shelby, buy that one.

Strife88

they shebly concept is the only other 1

this is a list of them, you sure you don't have a variation of one of them.

Callaway Sledgehammer Twin Turbo, Chevrolet Corvette ZR-1, Ford GT 40 MK I, McLaren F1 LM, RUF CTR "Yellowbird", Shelby GT-500, and TVR Cerbera Speed Twelve.Strife88

I have the shelby cobra GT-500 but they are all the same besides that

you have to own all 7 cars at the same time.Strife88

I was also confused with this achievement... mainly becuase I couldn't find a list that had the proper names of the required cars.

I would recommend you to do as I did, and just get every car that resembles the name in the list. 

gp19

tried it no success

I have all 7 cars but i didnt get my achievement.  I restarted the game and double check the list many times. Any advice?

look at the intercooler reviews at gamestop.com

There's an update you can download from xbox live marketplace that lets you play aac(itunes music files) on your xbox 360. They have to be unprotected though. I'm not sure where in the marketplace you can find it. Don't worry, the download takes only 5 seconds.UnrivaledSHOGUN

K thx u know anyway to play protected?