Alright trying to tackle a monster anyone ever seen on a 90 SC 5sp headgasket cause backfire?no antifreeze in oil no water out pipes no smoke replaced pretty much every sensor on the engine I know the head gasket is bad from a leak combustion test but I don't think it is causing the backfire and when I mean back fire I mean hard backfire blew the seam on my passenger Muffler doing 45mph in 5th not acclerelting