I just bought a used Big Gun for my 2001 YZ 250F and don't know if I should change the Carb Jetting or not. Does anyone have any experience with the Big Gun and carb settings. Appreciate any help I can get. FYI, I live in Virginia in the Shenandoah Valley if that matters.

Did you get the full system? I got the full race series system and went up one on the pilot and 2 on the main. Needle stayed the same. This jetting change was on a WR that is YZ timed, had the YZ muffler on it and all the free mods done. Basically I went from a 42 pilot to a 45 and from a 172 main to a 178. I ride at about 2,000 to 4,000 ft 60 to 80 degrees outside & dry. Hope this helps some.