Thanks for the excellent idea about an added solenoid at the throttle body. I recognize this approach from old GM carb setups, too. Since my car already has the idle moderated by the CIS system and its idle speed motor, I was hoping to come up with a solution that would stay within that system, rather than layer on an additional new system. My view of this would change significantly should my CIS system--or even just its expensive idle motor--suddenly tank. In that case, I will definitely be shopping for a boneyard solenoid.

Thanks again!