Hello, I have this issue and it is probably two found. Last season my rhino ran pretty well, It had a problem back firing through the carb at idle. I richened open-end up the mixture screw and that seemed to help, didn't get rid of it totally, but better. The rhino was built prior to me owning it and it has run well, has pipe, open airbag lid, I think 686 kit, and a cam. I was out last weekend, (sea-level) and it ran terrible, ie, back firing on the decelerations, almost stalling, and the backfiring through the carb is back. I cleaned it thoroughly, so I think, I have monkeyed with the air mixture, to no avail. I had the carb off 5 times while on my last trip.... can't figure this out. I feel like it is lean, I have a 55 and 175main jet in it. I looked for exhaust leaks, none that I can find. Runs great until full throttle, then when I let off it backfires, and wants to die. The plug didn't look so bad, I changed it, nothing. I am hoping someone can help. I have combed the forum, and would appreciate any help.