Don't worry dude, I have an OC'ed 7970 and it does the same to me. After all you card is there at 36C and 96FPS, what could possibly be wrong apart from BF3 doing things wrong?
But as the guy above wrote, when you change your GPU you got to remove the drivers and better also use DriverSweeper v3.2 and then reinstall them with your new GPU on.