[billinstuart]

Same problem, misfiring, 5.7 vortec, 140k miles. Just installed NEW heads (old ones cracked), polished rough edges in heads, cleaned piston tops like new, NEW fuel injection with electronic injectors, plugs, wires, distributor cap, rotor (all Delco or better, no crap), new thrust bushing in distributor, new crank sensor. no codes, cam retard ok, ran with GM Tech 2 scanner, everything normal. Popping is now WORSE with everything in great shape. disconnected EGR, no help. Can't drive over 60 without serious popping/misfire. Ran on ignition scanner..trace on primary side was perfect. Fuel pressure 55+ lbs. Replaced new injector system with old poppet valve injection unit..no difference. Really frustrated. Cam sensor in distributor just tells brain which cycle crank sensor is reading..at 2500 rpm shouldn't make much difference in injector pattern. TPS? Looked ok on Tech2. O2's were banging away. Short/long term fuel trim were ok. Cleaned Mass airflow sensor, no vacuum leaks, no slop in timing chain, distributor gear like new.

Frustrated as hell. It really feels like ignition problem, but nothing apparent. It's a small block Chebby..ain't new stuff. Someone out there MUST have figgered this out..talk to me!