All the info definitely helps, my Nat type is open. Ideally, you need to hardwire your Xbox to your router to give lag a spanking. Consider getting home networking plugs if your Xbox is on a different floor of the house to your router. Bear in mind that anybody in the home streaming live video and playing online on Live etc at the same time as you will affect your bandwidth. You'll only get an accurate test if you're on your lonesome.
I have also tried changing my connection type on Blops 2 to best. Strangely, I have experienced more lag on best than on normal. There is some weird lag compensation on best that I couldn't get on with. For example; I was playing Domination on Hijacked. I capped another player with nearly a full mag from my MSMC as he was running up some stairs. Then I died
On the killcam, I was just standing there in the doorway like a plum and he blasted me with his shotgun. The match continued in that fashion, which was a surreal experience.
The other lag I've experienced is when there is too much shit in the sky. Care packages r' us coming down, poxy enemy stealth chopper and UAV flybys all at once.