Tearing apart my engine, I've found a couple of questionable vacuum
hoses and replaced them.  But more importantly, I think my Auxiliary
Air Regulator was bad or out of adjustment.

I removed it from the engine, and at ambient temperature (about 65F)
the valve is about 80 - 90% closed.  After 20 minutes in the freezer
(about 0F) the valve is only about 1/3 open (I can push it another
1/3 open with a screwdriver).

After connecting it to 12V, after about 5 minutes it closes all the way.

So on the theory that I'm not getting enough air through the valve
when cold, I adjusted it to be open more when cold -- there is a
little nut that can be loosened and then you can adjust the cold
position.

The car seems to idle higher now when cold, althought the idle is
still rough.  I'll need to let it cool off and try again tomorrow to
see if this really fixed it or not.

Thanks for all the suggestions!