hi, my GTE has an annoying habit. when im driving in heavy traffic (everyday) my car kangaros at low revs, any idea's what might cause that? its only if im rolling along in 1st or 2nd below 2000RPM. also, my vauxhall mechanic mate says that my piston rings are on the way out (too much crankcase pressure) so, have any off you changed piston rings? how hard is it? i've done headgaskets before , so i know some engine stuff. Thanks!