I don't know if it should affect performance but it's much slower than 7300 and it shouldn't. And the only thing that changed since I switched the video cards was that, so it's a longshot but I got to try everything I can and there ain't much left, tried injectors (all I know), EFI strings (with EFI studio, OSX86Tools and manually) different kernels (10.5.2, 10.5.4 xnu and latest voodoo) and the same result every time.