I have an 02 wrangler. Recently the car has run at idle very rough. the sound is all over the place. when u rev it, it has a short sputter and then goes. when u get on it same thing. if ur in 3,4,5 gear and pin it, its got nasty backfiring through my magnaflow exhaust and it sounds like the axle is jumping. it pings really bad. we put computer to it and it is a misfire. is this typically what it should sound like. any other issues?