Looking to see if anyone has had this issue. I just finished installing new head gaskets and now the engine will not rev over 2500 RPM without popping and banging - This is with the accelerator floored. There are no knocks or ticks in the engine (other than the loud ass injectors) and it seems to idle OK. Here's what has been done to the engine: gutted front cats (this was done well before pulling the heads) heads milled .008 LMS head gaskets New head bolts New pushrods (Jesel 3/8, 7.6, .080 wall chrome moly) New valve springs (Comp Cams LS style) New valve stem seals Screamin Demon coils JTSV Performance wires (in the correct order) Champion spark plugs While trying diagnose: No CEL or codes (checked with key and cluster procedure, just says done) new crankshaft position sensor (guessing with parts) new TPS (guessing with parts) reinstalled old coils to eliminate new one from being defective (acts exactly the same as with the demon coils) checked the spark plug wires are in correct order double checked the ground wire on the back of the passenger head Gently drove the truck to put new fuel in. Didn't help. Next steps: I can't get my code reader to communicate with the ECU. I am going to plug it in my other car to see if it has died. But it makes me suspect an ECU issue. Testing fuel pressure (gotta buy the tool). See if the exhaust has plugged up further downstream, neighbors probably won't like this test. Put the stock pushrods back in. Would the heads being milled make the pushrods too long, holding valves open, but letting the engine idle and rev to about 2500? The truck was running OK before pulling the heads but was using a lot of coolant. I did find a crack in the head and had it welded. And then they were milled. Are there any other grounds? I have checked the one on the back of the passenger head, the one on the block, fender, and frame going to the battery. Other than a Magnaflow cat-back exhaust the truck is stock. Any suggestion are welcomed as I'm running out of ideas.