I was doing some reading around the forums for help with my problems running GT4 and all of the discussions about this game ended with the people having trouble running the game having someone explain to them that this game needs a CPU that is 4.5GHz + to run smoothly. Well, this is simply not true as I have achieved great framerates with a high resolution setting and texture filtering. The game looks great on DX11 and runs like butter. It took me a little tweaking but I figured it out, I think it may have something to do with the MTVU... Someone who knows more about this stuff than me could probably do even better, I was just tweaking around with it and all of a sudden my game was running smooth.
My specs- AMD Phenom II x6 CPU @ 3.2 GHz | 8 GB DDR3 PC 1666 | Nvidia GTX470 1280
My specs- AMD Phenom II x6 CPU @ 3.2 GHz | 8 GB DDR3 PC 1666 | Nvidia GTX470 1280