Turned out to be an easy fix.

Made sure connecting the hose from the main T to the shutoff valve woked
Connected the gray line that goes to the "ignition" switch right to the T and sure enough it worked too

Now the only issue is that the vacuum doesn't bleed out of the circuit fast enough, so it's impossible to re-start the engine right after shutting it down. I guess I need to take a needle and poke the rubber hose to fix that.

Do I understand correctly that the hoses I've disconnected were for door locks and maybe cruise control? This is a manual transmission 240D.

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'81 M-B 240D 4-speed 132Kmi
'98 BMW 528i 5-speed/sport 125Kmi
'93 VW Eurovan GL 5-speed 166Kmi
'00 Hon RC51
'04 Suz SV650 track dog
'89 Yam FZR250R