I disconnected everything and pulled the blue vacuum amp. There IS an adjustment on the underside, covered by a black cap. The adjustment DOES change the behavior of the device, because I tried it with the MityVac. Unfortunately I am having difficulty determining whether or not it is bad. If I pull on the VCV port, I get a humming sound from the device and the vacuum does not hold at all. The Mityvc holds vacuum very well if I draw on the pressure port (PRE with the retainer clip). If I plug the VAC and TRA ports with my fingers and pull a vacuum on the VCV port, the vacuum leaks down at 1" Hg per second. If I cover the VAC port and pull a vacuum on the TRA port, the vacuum rises to 5" Hg and will not go higher (makes a humming sound if I try). The pressure port seems to hold positive pressure with a gradual leakdown.
I tried making the adjustment on the injection pump device and, before I disconnected the blue amplifier, I noticed a change in top level vacuum as was described in your article. The vacuum levels still did not drop as expected when I pulled the accelerator linkage.
Similarly, with the line to the VCV left wide open, which should produce vacuum at the modulator port at the boost threshold, the modulator vacuum did not drop as expected. Turbo boost did result in some drop of the vacuum.
I am interested also in where the "source tee" is that you mention briefly. Which source are we talking about here, and where would the vacuum restriction be that is supposed to prevent a high biased vacuum?
1987 300D Turbo 229k (+)