The only vacuum connections covered in the US M116/7 manual for that vintage are the lines between the throttle body and the swtichover valve and the switchover valve and the distributor. The throttle body connection is in the middle of the switchover valve.
A diagram in the fuel injection system section suggests that there's a retard line between the rear side of the throttle body to the rear fitting on the distributor vacuum advance unit. This diagram doesn't show a switchover valve along the advance line.
There is some mention of a fuel evaporation control system. There's a mess of hoses in the fuel tank area and one hose that leads to an unspecified location in the engine bay. The hose looks more like a fuel line than a vacuum line.
Aside from the hard plastic(?) line to the brake booster, the other vacuum lines around the engine are probably for the central locking system. I don't have an R107 manual to validate this notion.
If your car was brought into the US, maybe it was retrofitted with emission contol equipment for a later model year.
I replaced the fuel injection wiring harness of my dad's US spec 71 300SEL 3.5 and I don't remember there being a lot of vacuum lines. Certainly not nearly as many as on my US spec 78 450SEL.