Lookin for some help on this one , 2010 gmc. 5.3 , towed in for bad missfire , cyl 4 and 6 , check plugs , coils , injectors , all good , cmpression all 140-150 , leak down test around 10% , running compression all 150psi except cyl 4 50psi , pull right head , replace AFM lifters , (cam is good as well }.. .. missfire on cyl 6 gone , still mission on cyl 4 , ,, pull head again , slight bend on intake valve stem , in cyl 4 , replace intake and exhaust valve , , still missing on cyl 4 , still has low running compression in cyl 4 but good static compression @150psi and leak down of only 10% .. any thoughts