Just thought I'd give an update on my idle problem as it may come in
handy for those searching the archives trying to solve the same.

It turns out the connector that I could not identify goes to the idle
stabilization control unit as Mark D had pointed out in Bentley page
24.54. The wire is supposed to exit the wiring harness which then goes
into a connector. It then goes back into the harness. My problem was
that one end of the wire had frayed and broke right where it came out
of the sleeve of the harness. Initially I never saw the nub. When I
saw the illustration  in Bentley I knew to take a closer look at the
harness.

I had to cut the harness back to expose enough wire. After repairing
it and reconnecting I started the engine up. Success! The idle was a
bit rough for a few seconds but smoothed right out.

One note. A number of people checked there vans and didn't see the
same connector. Turns out it was moved to the right side of the engine
compartment after 9/87.

Thanks to all who offered help and suggestions!

-Mark