Well, I am glad the texting while driving police did not see me. I drove around and here is the story.

Starts and idles at 9 inches. When you touch the gas it goes down immediately to about zero-2 inches (Mityvac has a box that says zero which appears to cover everything from zero to four inches). At full throttle it is about zero. While driving/coasting it registers about 9 again. It upshifts smoothly in the zero psi box. But the downshift is at 9inches again and is a clunk.

So - idle at 9inches
drives at 0-5inches based upon throttle - more throttle = less vacuum
upshifts at 0-2inches smoothly with normal throttle
downshifts at 9inches with a clunk whether this is coming to a full stop or just downshifting from third to second.

Seems to me that it is bleeding down perfectly in response to throttle. Should I try turning the modulator CCW about one click? Two clicks? Quarter turn?

Diesel - in response to your question I think your modulator is leaking. Mine pumps to 25inches and holds it; no leak at all. At least for about a minute or so until I released the pressure. Indy tells me he installed a new vac modulator when he installed the used tranny.