A while ago, I put a new EVGA Nvidia GTX 650Ti BOOST 1GB in my MacPro3,1 so I could run Lion and later. I didn't flash it for EFI, but it worked anyway, and I didn't care about having the boot screen. The ATI 2600XT my Mac originally had was a decent card, but for some reason, it was nearly unusable with Lion. The GTX worked fine with Lion+, but I tried some graphics-intensive things on it, and it wasn't that much faster. My brother's weaker MacPro1,1 with some older Apple-branded (i.e. EFI flashed) ATI card runs games much better than my Mac does. Now, my new GPU is primarily so I can use my computer for work (Xcode requires 10.10), but I occasionally play Counter-Strike: GO and would like it to perform like it should! Finder animations also lag sometimes, but that might just be Finder being Finder. BUT my card seems to run great when I boot into Windows (which I can't do anymore, but I'll reinstall Win7 later maybe just to test again). So I'm thinking that flashing it for EFI would help. Everywhere I've seen, people say it doesn't help besides adding a boot screen, but I'm doubting that now. Any thoughts?