Okay, this really *does* deal with my mileage problems and not my weird stalling issue.

For one thing, I think my idle has been set too low. My oil light has been popping on when the idle has dropped to it's lowest level (my guess is <500 rpms).
I the dialed the idle up to about 800-1000 and checked my intake vacuum.

While running, I attached my vacuum gauge to my center-most PCV nipple.

At low/normal idle I was greeted to a very bouncy 14-18 inches of vacuum through a 5/16" inner diameter hose.

This gauge came with a 1/8" rubber hose, but I had nothing to attach that to on the engine, so I substituted a small rubber tube and a 5/16" piece of hose.
So, I'm unsure if the measure is correct, but I do assume that the way the needle was bouncing is not a good sign.

Reving the motor up to 1200-2000 rpms resulted in a stable needle reading around 20 inches of vacuum.

If I remove the hose altogether the idle rises significantly and stays high - I guess that's normal since the carbs are essentially "powered" by vacuum.

So, what am I to make of the extremely "bouncy" vacuum from the intake at idle?

Suspect the valves? The lash was adjusted recently, so I don't think it is is just out of adjustment. My recent dry compression test results 160-170-165-160 is somewhat down from my test several months back with the same cylinder head when I got 175-180-178-175...

Is this valve recession or something more sinister...?