Problems with Gigabyte GTX 460 V2

Hey everybody ! I got my Gigabyte GTX 460 1GB V2 today .
I installed it corectly , applied the latests drivers and rebooted the system . Now the funny thing is that the performance seems quite a bit slow ! Like GTA IV runs maxed with only 22-30 fps , the same as my old GT440 did . Bad Company has everything maxed and its set with 8x aa on and it is running between 45-70 FPS , but there are strutters and also some noticable lags . I am running on 1280x1024 resolution and Pentium G840 sandy bridge CPU with a corsair CX430 V2 PSU and 4 GB DDR 3 ram ! Is it some kind of bottleneck or is it some kind of driver problem ? I would really like if someone could help me fix this problem as i am having a little depression because thats not how its supposed to run !