Ok here's the low down I got a 89 mj 4.0 renix auto trans this thing has had a full tune up and then some I replaced a bent push rod and put a high output head on it and there's no power at wot it will idle and sorta drive put it mostly pops sputters and backfires at anything over an idle HELP PLEASE

 

Did you get the ground strap back on the at the back of the head?
Could be a bad TPS. How did it run before the head replacement?