Guys, I have read several posts here regarding idle fluctuations and engine stumbling under load. I am having the same problem and I have done darn near everything I know to do except replace the intake manifold gasket(and I really don't want to have to do that). Below is a list of things done to the '90 Trooper w/2.8 six cylinder:

New fuel filter
New plugs & wires
New distributor cap and rotor
New coil
Timing checked
Checked egr valve
New O2 sensor
Seafoam poured directly into the throttle body and into fuel tank
Disconnected Temp. Sensor (made no difference)
Attempted to check vacuum hoses although I really didn't find very many

What am I missing other than the intake manifold gasket?

Any ideas?