Thanks for the information.
I talked with my service people. They actually swapped out the ECU (more specifically CIS-E) with one they had laying around and the problem disappeared. And as you and they say - the idle control is integrated with this unit. Armed with this knowledge I'm willing to plunk down the $500 on a used one. I don't have to give up my old one in this deal.
The throttle switch I can't be sure of but I think it works and here's why I say that. At highway speeds you let off the gas completely and the car begins to slow but about 1-2 seconds later it really begins to slow down. This delayed action does not happen if you rest your foot on the pedal just a little bit. Is this consistent with a working throttle switch?
As for the control valve - I just don't know.
Thanks again for the clarification and I will post again so there is a complete case history through resolution on this one.