Router, NAT, and lag issue

I have had the Linksys WRT54G router for years now and every game I play is fine. However, I am lagging big time in Gears of War 3. My friends are fine but I am bouncing all over the map. Here are my questions:

Says my NAT is moderate, can this cause lag b/c its not open? I have never had a problem joining anyone or talking to anyone on Live. If I open my NAT which is the safest way to do it, DMZ, port fowarding, something else?

I know it would help but do you think it would solve my problem if I wired the router to the XBOX? Does NAT not apply if you are wired? Is lag caused more by my xbox being wireless or my ISP.

Why do I only lag in Gears? I am fine on all other xbox and ps3 games?

It is strange that it is only doing it with Gears 3. You could try a wired connection, or if you want to keep wireless make sure UPnP is enabled on your router settings.

Also found this on 360 help page:

+ NAT problems do not affect game play speed. A NAT warning affects the ability to connect and communicate with other players.

+ You should not experience a NAT warning if you are using a wired modem connection.

Also I just read that Gears 3 uses dedicated servers in ranked matches, so try a ranked matches as you might just be getting a poor connection with P2P.