1995 5.7 engine miss

I have a 95 p/u with 40,000 on rebuild. The motor will flutter miss at idle in park but is more noticeable in gear while holding the brake. Only at idle though, if u gas it at all it seems better. I have replaced the distributor, cap, rotor, wires, plugs are fairly new, iac, egr, and coil. I checked fuel pressure and I have about 12psi. Sprayed brake cleaner around intake and throttle body to check for gasket leaks, found none. Sometimes the miss is great enough to kill the motor but it always fires right back up. Sometimes it runs fine then misses a beat and is fine for a few seconds then misses again. It will repeat that until it misses enough to snub it out. HELP!! Im in over my head now and cant afford to keep throwing money at it.

Is this a Vortec engine? What brand and part number are the plugs?

It is not a vortec and the plugs are autolite. Not positive on the # but i think they are #26