If you look in Dave Sponaugle's tech gallery, you might be able to find the connector you are decribing along with an explanation. Otherwise you could try and post a pic of the plug so we can get a better idea of what that connector is.

However, I believe there is a 2 tang temperature switch that threads into the front of the passenger side head that provides temp signal for the high idle/cold advance. Its kida hard to see and you have to look down the back of the goose neck for the thermostat housing to see it. I'm not completely familiar with the 87 and up controller wiring, but since its not threaded directly into the water jacket like the older ones, its possible that this is used as the temp signal instead.

This might help:


This covers 1987 up to 1994 IDIs
Looks like there is an outside temperature switch (closed when cold, open when hot), so that loose connector could be your problem.