On the back of the injection pump is a valve that I call the proportioning valve. It is a controlled leak, proportional to throttle movement.
Where are you taking the vacuum reading? What is it at idle? How does it change as you move the valve linkage? If verything is correct the valve should make no difference, because the throttle is at idle and the micro-swicth is not feeding the vacuum to the proportioning valve. Try moving the throttle link (do not raise engine from idle). When the micro switch engages there should be a significant drop in vacuum. If you hold the throttle in this position and move the proportioning valve linkage the value should go to zero at full throttle.
What do you have??
None of the transmission vacuum should have anything to do with how long it takes to shut off! They should be on separate vacuum circuits with the source being the only thing in common.
Bosch Master, ASE Master, L1
33 years MB technician