You cant change the voltage on Asus video cards with MSI afterburner. Asus (unless they changed it) locks it to there software only. And dont stress about the performance, this beta is no where optimized. Shows worst on ATI cards I think. Just run with few AI cars and online only. I notice the Maganes and GT cars give me the worst performance issues. I'm run Crossfired 5870s and an I7 920 @3.8 everything maxed but all AA is off @1080. Starts off at 100FPS until you add AI cars. its like it drops 8fps per car.