My dad has an 04 ltz and it was running lean. He has a Yoshimura slip on, and k&n filter. With the stock jetting it would backfire when letting off from full throttle. The spark plug looked really lean. I just installed a 6sigma jet kit. Moved the clip position down 1 slot, installed the recommended 146 main jet, and 27.5 pilot. Also set the fuel mixture screw to 3 turns out. After finishing the carb work it started right up. Sounded like it was running smoother than ever at idle. When he revved it up it sounded great and didn't backfire at all like it used to. We also had the airbox cover off, as recommended with the jet kit. My dad took it for a spin and he said it felt like it would bog ar high rpm in 1st gear. We installed the airbox cover and I took it for a test ride. I noticed the bog or power loss at high rpm in 1st gear. Adding the airbox cover didn't seem to matter, all though with the stock jetting it wouldn't stay running with the airbox cover off. Well it got late so we had to stop for the day, but my Dad did notice afterwards that the fuel valve was in the prime position. He said he's heard that you shouldn't drive it in the prime position and I'm hoping when he tests it out tomorrow it runs great.