unless it is misfiring and you ae getting a p300 code, dont bother...p300 "multiple misfire" is a goosechase..burnt exhaust valve, cps, tps, o2 sensor 1, or plugs/cap/rotor...if its just valve slap, then pull the head and lap the valves, change to mopar performance springs ,are suppossed to be 120# at 1.640. They have a 270# spring rate.