How do you unlock the BMW m3 gtr in career mode of need for speed carbon?

You cannot drive the BMW GTR in Career Mode except during the intro where you have to escape from Cross. The only way to get it into Career Mode is to hack the game. You can unlock it for Quick Race by getting the 4 Reward Cards for it. If you wish to drive the BMW GTR in free roam without hacking your game just select Quick Race and go to Starlight Street, then turn around and go through the shortcut. NOTE: There are no traffic or cops in Quick Race.