I’m currently having the same issue, at idle my rpm’s drop and then Increase, I can also feel a slight misfire while in park. I’m going to test my pressure at the throttle body today. I’ve done everything you have done as well
1994 Chevy c1500 5.7 TBI
I’ve been chasing and intermittent misfire and loping idle with my truck.
I replaced and tested the Engine coolant temp sensor
New EGR and solenoid.
New MAP sensor
New IAC
New TPS
Replaced all fuel lines, new pump, rebuilt throttle body (with gaskets) new...