It could just be that ethanol fuel, but i'll get a SES light thats says its running lean, and if it idles below 750, theres a bump in the idle every sec or two, sounds kind of cool to me, but i know this is not good. it has 80k and I havent done any of the "100k mile s***". like fuel filter and the whole 9 yards. Once I got it stuck in the mud and got it really hot, it almost sounded like it was misfiring on 1 cylnder. Could be the intake mani gasket since its really hot where i live and I have a WAI. but i hope not