No the part he is talking about is in the bottom of 5 on your diagram, and it's almost not mentioned in the fsm. It is a pure thermostatic air valve to raise idle speed after a cold start for only a few seconds, at most about 2 minutes when it's really cold.

The ISC is a whole 'nother animal, #2 as you inquired, with it's own set of problems. The old brown body units were known as frequent fails. If you used a throttle body cleaner, it ate the insulation off the windings of the stepper motor and shorted it out, which could fry the ecu in some cases. This is why the fsm directs you to plug the air passage before using such cleaners. There is a revised replacement with a black body that is much more robust and longer lived.

Dave, I get to say, "Tojaso, tojaso... <img src="/forums/images/graemlins/butwiggle.gif" alt="" />".

I wonder if you couldn't just fill the fidle passage with epoxy and call it done. I don't think that the function is all that necessary except for cold start emissions anyway, and since the part is as far as I've been able to determine, not available at all except as a whole throttle body, which is damn expensive as you found out, ditch it. Now if we could just find just the little thermostat and figure out how to install it...