Help Needed for Euro Head Light Vacuum Hoses - 1989 420 SEL

I'm trying to hook-up the european headlight vacuum system on a 1989 420 SEL. I'm not sure how to hook-up part number 126 800 10 78, a vaccum valve that is supposed to be located just prior to the dashboard height adjustment
switch, on the vacuum supply side. The part has 4 nozzles on it, numbered 1 to 4, and #4 has a yellow dot. Which nozzle should be connected to the dashboard valve and which nozzle to the vacuum supply? What are the other 2 nozzles used for?
Thanks, Joe

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