Intermittent Misfire 1995 Metro LSI 1.3L

[RBlackmon]

My engine runs well most of the time, but I get intermittent roughness. It will idle smoothly for, then hiccup. It occurs most at idle rpm, but somewhat at higher rpm. I also get a 51 EGR code. Checked out the EGR, cleaned it and replaced everything moves freely. EGR is vacuum controlled and vaccuum comes from intake manifold to a three-way solenoid valve then to the EGR Modulator, then EGR. Cleaned everything, but cannot tell if 3-way switch is working. My Hayne manual give little info on this switch. Performed a full tune-up (plugs, wires, cap, rotor, coil, fuel filter, belts, etc) plus compression check and timing belt, but no change. Went to Precision Tune and they said I had an Intermittent drop on cylinder #4 and needed a new distributor. New distributor made only a marginal difference. It has 168K mi

[RBlackmon]

UPDATE! Went back and rechecked all vaccuum lines from throttle body to TWSV to EGR Modulator to EGR. All clear. Checked intake and exhaust to EGR...all clear. Verified EGR Modulator good per the Haynes Manual. Verified EGR diapham good with vaccuum pump. Only thing I have not done is apply 12v to TWSV to verify it shifts. I cleared the trouble code and started up. It still runs intermittently rough at idle. Cant tell if it is fuel or spark. Its almost like the ECU cant make up its mind on Fuel or Ignition timing. Someone please HELP!!!

[hvdragon]

check IAC/ISC valve