SLI problem and performance problems?

I bought a lenovo y500 with 2x650M sli.it worked great but everything went horrible after i updated my graphic card to 335.23, it destroyed my laptop (Often freezes, unable to view pictures, watch videos, and play games). Anyway i sent my laptop into a PC shop, i got it back with all the SLI and **** but its performance was noticably lower than before. Everytime i stared at particles (shadows or trees or fires) it becomes 15 fps or worse. Before 335.23 ruined my laptop i could stare at those particles just fine.anyway i thought updating my graphic card would solve the problem but when i update it to 337.88, my SLI was gone. Its not in my nvidia control panel anymore nor in my device manager.
so how do i get back my performance and my SLI.

Contact customer support. Truthfully, half of the people here don't even know what a CPU is, let alone knowing how to fix your problem.

Seems like a drivers issue. They probably changed something in it that disabled your SLI or reset your settings.

Uninstall the drivers, then reboot into VGA Mode, then install the older drivers. If it still happens, it's not the the drivers.

Overclock it