Thanks Brian!

I'm not sure where to go next.
Here's what I did:
1. cleared codes
2. Started engine, pulled vacuum lines one by one of the TBI to see what effect it would have. Some of them changed the idle slightly, and then I put my finger over the port on the TBI, and it would act just like as if the hose was in place. Other hoses, did not change the throttle when I unplugged them, and left them open.
The big difference came when I unplugged the vacuum hose that comes from the rear of the TBI, and plugs into a sensor (MAP?) beside the TBI. When I unplug that, the idle drops considerably, from the sound of it, near a normal level.
3. I didn't understand your IAC advice. The screw I think you're talking about is the one that sets the position of the throttle blades when the throttle is closed, right? On my engine, it is already backed out all the way. I backed it out about a 1/4 turn before the screw pulls away off the throttle bracket, because the blades are already touching the sides of the bores in the TBI.

How do I set the IAC now?

I wonder if there might be a break in my base gasket under the TBI....I've traced all the vacuum lines I can find twice now, and they all appear plugged in where they should be.