Inconsistent idling problem

You keep mentioning that engine temp is part of the issue... At a glance I didn't see if anyone suggested or asked if you had the thick insulator base gasket. If your heat crossover in the intake manifold is functional it can get hot very quickly. Also if you have stock exhaust manifolds the heat riser plate in the passenger exhaust manifold may be sticking or partially blocked causing extreme intake manifold temps that will boil the fuel very quickly.