This seems to be a sticking point of confusion for people.
1. There are several incarnations of these vac valves, single, double stacked, double flat, etc, etc. Depends on year.
2. I can tell you for sure on the double STACKED models, one is for EGR, one is for shift control. And by shift control, it shunts HIGH vacuum to the modulator at closed throttle for obvious reasons.
If they leak, it'll screw things up, as Will has found. If your patient and your tranny/bleed valve on the IP are in good shape, you CAN do away with them, but it's a *****. It lessens your margin of "error" in your vacuum curve, that fine line between feeling downshifts and too soft light throttle shifts. If you hook up a vac gauge to the line to the tranny modulator and just do open the throttle on a car with functioning valves, you'll see the vac dive from 17inches or so down to about 10 as I recall, WAY faster than the bleed valve will move it on it's own.
I will never EVER own another automatic MB.
Glad your up and running Will, now let's fix those oil cooler lines!
