Ok so I bought the 4 cars it says I need to buy and now I dont need what the other 3 cars I need to buy are because it says I need 7 exotic cars in all? What cars do I need to buy? Let me know thanks ahead of time for the help.

All seven:

1) McLaren F1 LM
2) Shelby GT-500
3) Ford GT40 MK1
4) Corvette ZR1
5) Callaway Sledgehammer Twin Turbo
6) TVR Cerbera Speed Twelve
7) RUF CTR "Yellow Bird"

Also, check out this thread. It's all the info we've put together about PGR3 achievements.