660ti GPU Utilization Is Just 42-58 % While Heavy Games Like BF3 GTX 4

GPU utilisation is just 42-58 % while heavy games like GTX 4 episode from Liberty, also in crysis 2 many times it is just 70-80% at 1600*900 resulution and quality is maxout in COD MW3 and black opps it fails to maintain 60 FPS constant in Battlefield 3 Armod kill utilization is just 43-73 % while FPS are below 30-45 and why effective memory is 3000 Mhz instead of 6000 mhz

while few days back my gpu utilization was 90-110 % in bf3 but in 2-3 days it is making me sad why gpu utilisation sucks in most of games while it was working fine during 1st 5 days when i buy is my gpu is half-Dead and go for replacement ?? my specifications are i5-650 , 16 gb 1333 MHZ ram , and PCIe 2.0 slot and 3000 mhz memory is a problem of PCIe 2.0 ?? [URL] and many times it underclock gpu , utilisation 30 % and fps 20 , hollyshit I think i made big mistake buying gtx 660ti instead of HD7950