[damien c]

this is going to sound really stupid but have you got the sli bridge on the correct way as sometimes if, it is on wrong it won't work i have found that out in the past with all my sli rigs, also have you enabled sli in the nvidia control panel.

what i would also do is for the games that you play try googleing the command that you would enter in to the console, usually the tilder (`) key in game for increasing the max fps i know on call of duty 4 the default is around 80-90 and i have mine set to 200 and i max it if i set to 250 i hit 260fps, other than that i not sure other than perhaps see if there are any new drivers for the cards.