Gtx 590 problems

Ok so I have this weird problem going on with my system. I recently purchased a gtx 590 and I noticed in games like Crysis 2 I wasnt getting anywhere close to the fps others were with similar rigs. I came to the conclusion that I was being cpu bottlenecked (using a 1090t @ 3.2) so I decided to purchase a cooler master V6 gt and overclock to 4ghz and then suddenly my fps average in Crysis 2 shot 15-20 fps and I was very pleased but theres now a new problem. In some areas of the game where it should be very easy to run, my fps stays about the same and when I look up at the sky the fps shoots to 100 but will not move any higher at all like its being capped. I uninstalled and at first my fps was amazing and i was getting over 200 looking at the sky and then very shortly after loading and closing the game throughout the day the fps 100 cap was back and things seem to be limited at times. Im very confused as to what this is, seeing how I fixed my bottleneck. Any suggestions? I've also noticed this in gta Iv where sometimes I can get 60-80 fps on a certain area and the next day that same area I get 25. wtf??   System specs: Motherboard: ASUS M4A88T-V EVO, RAM: 8 gb Corsair xms3 1333 overclocked to 1600 @ 1.65v, CPU: AMD Phenom II x6 1090t BE overclocked to 4ghz @ 1.425v, Graphics: ASUS gtx 590, Power Supply: AXP-800R14HE 800 watts. - Please help this is strange...