My '92 expl. spark knocks so bad when i run reg. unleaded fuel it sounds like a diesel,a crappy running diesel. premium gas has become too expensive. Has anyone else had this problem and if you have, how did you fix it? Some people have told me it won't hurt it to knock like that,but man--it can't be good as loud and strong as it is. Any help would be appreciated. Thanks,Jubil22 :p