I believe I may have a vacuum leak that is apparent at lower RPMs.
There's no real drivability problems, but there is slight RPM hunting
at idle and my vacuum is 12 in Hg at idle, moving up to 19 in Hg when
I open the throttle a bit.  I'm a novice, but it appears to me that
there may be some leak.  I can't isolate the leak with carb cleaner.
Maybe there is no leak?

I've heard that people change gaskets on the throttle body.  What
gaskets are there and where can I get replacements?  I notice that
there is a hard piece of plastic between the center air plenum (hollow
metal box about the size of a shoe box) and the throttle body.  I
suspect that this gasket was maybe softer at some point in its distant
past?  About 2 months ago I solved some drivability problems by
coating both sides of that gasket with silicone rubber and
reinstalling it.  However, I'm wondering if it is still leaking.  Are
there other gaskets?

I've changed all the rubber hoses and I have hose clamps on most of
the hose connections.

Also, is this 12" Hg at idle normal?  When the engine was warm, it was
at 8" Hg, but after about 5 minutes, it got up to 12" Hg.  After the
freeway drive, it was at 12" Hg at idle.  At higher RPMs, it's 19" Hg.
 I've got the gauge tapped into the fuel pressure regulator vacuum.

-- Craig