Vsync on 
I would bet that if you tested online with vsync turned off you prob be pushing 140 to 180 framerates...... they would just fluctuate more up and down......
my old ASUS EAH 3870 512meg card pushes 158 FPS with a little fluctuating down to 140's in hvy areas with vsnyc turned off in game .everything set to MAX and shadows set to what is it? 2048? using hires pkg & 1280 x 1024 screen res with vsnyc on it is maxed at 75 hz solid 99% of the time...... on my DELL Ultrasharp 19" LCD......
did that just to test to see what my card was capable of, and did not experience any tearing or stuff..... but I play with vsnyc on, and synchronized with my monitor refresh rate.....
just saying.....
edit: am glad it is all working out for you 38ruk
