If your not playing online, you could shut avg down before you play ( in fact shut down every thing you don't need) See if it makes a difference. I found that when I went back to medal of honor airborne after cod4 I thought the game was slow and camera angle rather odd, it was just that I got used to the way cod4 did things.

I doubt more ram would cure it, try and see if you have other programs running in the background that may be slowing your pc down.