XS,
Quick question.. Do you have 1 360 in the DMZ?
Nope, I am not a fan of DMZ, so am reluctant to use it, I prefer security over lag, lol. I thought about it but its not worth to me to make one of my Xbox vulnerable to being hacked even if its highly unlikely. Anyway thanks for the tip.
It is probably just coincidence but I have been seeing a lot more lag even playing solo since disabling PT. My son and I played a few games the other day, I was doing good and he was lagging real bad so he quit playing, so I stayed in the same lobby with the same players and played solo, lag was real bad and I think I went 6/14! Wow! previous games I was positive!!! Anyway next time one of us stops playing I am going to back out to the dashboard and log back into to MW3 because it screwed something up in the lag compensation dept. by one of us quitting.

I think MW3 is just broke and I should just give up tweaking stuff but my OCD won't let me.

Would be interested to review your router settings with you via teamviwer sometime. 
Me or Frag?