I have a 2000 arctic cat 500 4x4 shifter and have recently purchased highlifters performance kit which includes a supertrapp IDS2 pipe, K&N filter with outerwear. Since there is no jet kit available I have to guess on jetting. The sock main is 145, I have installed a 157.5 main and raised my needle 1 clip. I live at sea-level with a temperature around 50 degrees. The problem I am having is confusing, so here it is. It seems to work okay a sea-level but I recently rode at about 2500 feet and experienced poppin at 3/4 throttle and higher with a load on it (mud boggin') I pulled my plug to reveal a white plug like it was a lean popping. why would it be lean at 2500 feet but seem to be okay at sea-level. If anyone else has installed this kit what jetting are you running and does it work? I would appreciate any in put someone can give me. by the way I have 7 discs in my pipe. thanks, poncho