I'm not sure whether you have tried it already, however I recommend you do a clean install with NVkush, NVinject selected, do not install any other efi strings or enablers other than the two mentioned, just NVinject may help get maximum supported resolution but might not support "quartz extreme" and "core image" which is essential for Apple Front row and many other graphically accelerated apps like the album art browser feature in Itunes and NVkush does the trick, specially for Nvidia 8 series.