Looks like intermittent shut off prob is solved for now. I was checking some vac measurements again. On the the valve up by the brake booster I disconnected different lines and measured vac. Both nipples before the white valve measured about 12-15hg.
There are two nipples on that white valve. One goes to the VCV and modulator, and the other goes to lines going back into the cabin.
I stumbled onto that when I switched the lines on the two nipples that it would turn off on demand consistantly and instantly instead of only turning off 40% of the time.
Why this works I don't know cuz both holes have the same amount of vacuum measured at idle. They also have the same amount of vacuum if you pull the lines first, start it, turn ignition off, and measure with ignition off and engine running.

Trans shifts seem reasonable. I am getting a measurement of 15hg on the main line coming off the pump. Is this adequate? Some step by step guides say 15-20, others say to troubleshoot the pump if you are not getting 21+ here.

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.