2000 RPM stumble aqnd backfire

88 MJ 4.0 pukegoat tranny..........

I have the dreaded 2000 rpm stumble, does it when hot or cold. mild tailpipe backfire. I have changed the map, tps, O2 sensor, cap,rotor,plugs and wires and cleaned all the sensor connectors..still does it. The center plugs ( #3 and 4) are burning very lean, the others are a very light tan. I'm thinking fuel problem or loose intake manifold...any words of wisdom?

Its more than likely your EGR, classic renix symptom. Check to see if the rod goes up and down in the bell shaped valve on the manifold. and to make sure the vacumn line and the solinoid are good on the drivers side inner fender.
I think you can plug the vacuum and see if it helps. Good Luck

I thought so too xjing, but I plugged it off...no change.
Forgot to mention that I have the Mustang 4 hole injectors....little bitty holes....maybe plugged.