Did you thoroughly clean below the area where the EGR valve mounts that feeds into the intake manifold? Plugging up with carbon there seems to be a common problem on those engines. Also you might want to check operation of the EGR solenoids. There are 4 wires on the plug going into the valve, A through D. It looks like "D" feeds +12 volt into the solenoids on a common rail via a 10 amp fuse and the computer grounds pins A through C to activate each solenoid as needed. This suggests that the solenoids can be checked for continuity using an ohm meter. You can also see if they click when fed voltage. (Online sources suggest using a 9V transistor radio battery for this.)

(Disclaimer: This info is from searching online and using rockauto.com to determine the type of electronic EGR valve your engine is equipped with. I do not have personal experience working on that engine or EGR valve.)

As far as diagnostics, is it that the connector is broken and the wire is still there, or is the wire missing? If the wiring is still there you should be able to go behind the connector to jumper the wires and get the computer into diagnostic mode.

If you know of a mechanic with a Tech2 scan tool, that should be able to read any data the computer has to offer, but I'm not sure whether the problem with your diagnostic connector will be an issue. Looking at the connector pinout the "E" and "M" terminals are used for serial data communications which I believe should feed the Tech2 but I don't know for sure. (The only OBD1 car I've used my own Tech2 on was a '95 Saab and that had a different type of diagnostic connector under the passenger seat.)