Do me a favor and leave the EGR together for now. Confirm if it has two vacuum ports on top of the diaphragm. If just one then it is Federal. Put a vacuum hand pump on the vacuum nipple and confirm when operated, that it nearly stalls the motor or actually does. If nothing happens, then assume the diaphragm is leaking (not as likely as the next bit), or the passage in the Intake manifold is plugged with soot/carbon.
You can delete it if you want, but spraying brake cleaner near it may confirm a leaking diaphragm and a spot that idle surge could be created by. Leave fiddling with the EGR till last if I were you.
When you say the passage in the intake manifold are you referring to the hose that goes from the valve cover to manifold (pcv valve spot)
In the intake manifold where the EGR bolts to the side, is a tube - should be hollow. If it is plugged, clean it out. Its the bump in the runners.
Any standard you need the car to get to, should likely only be Federal emission standard. Confirm with your VIN via Mitsu dealer and/or emissions decal on the hood.
One of the EGR nipples will hold vacuum with slow bleed down, and the other will not hold vacuum IIRC. This is going off nearly a decade ago, the manual should have a test for this.
Any way you look at it, if you use a screwdriver/flat tip to actuate the diaphragm in the EGR and the engine stumbles while running, it is partly a good sign. You can plug the EGR vacuum lines for now if the temp valve (at the thermostat neck) is not hooked inline again (missing nipple).