Trying to SLI two 660TIs, doesn't seem to work properly

Just to clairify some things, I am running Win7 with a EVGA FTW motherboard and two MSI 660TIs (OC power edition). I have everything up to date as far as drivers and bios goes, everything can handle being put in SLI, but for some reason they won't play together nicely. One will only do PhysX, and if the game doesn't have PhsyX then it just sits idle while the other GPU is maxing itself out. I have tried to turn it on in the NVidia control panel but there is no where to do so. What am I missing?. Thanks in advance!

Does it come up as sli enabled in gpu-z?

I would uninstall drivers, run driversweeper, reinstall latest drivers just to be sure then go from there.