Odd Problem

I have a 1987 Bronco II with a 2.9Lt. It runs great expect for one thing. Every now and then, it seems pretty random, it starts studdering. The RPM gauge dives suddenly, then goes back up. Sometimes it gets worse and the motor completely dies and won't start again for a minute or two then it will start studdering again when it does fire up. I have replaced all the fuel filters, spark plugs, cap and rotor and also my air filter. I have also checked the ground wires on the back of the heads. I'm starting to wonder if it could possibly be the coil but I want to try and not throw to much money at it.

Any ideas would be great!!

check for carbon build-up behind the throttle body .
there are egr ports there and some times they clog.

I'll check that out. I have taken the egr right off and just put a plate over where it was mounted with a gasket to block it off. I have taken the vaccum line that was on the egr and ran it into the "map" sensor (i believe that is it's name) that use to have a vaccum from the egr to it. It has been running great and has not studdered yet. I have also replaced the ground wire on the coil, the one that was on there didn't look all that great.

I am now playing the waiting game.......

The MAP sensor needs direct manifold vacuum. The EGR is actuated through a solenoid valve. If you removed the EGR valve, plug the end of the hose. Running without EGR will set a trouble code if the valve has a sensor on it.