The important vacuum to watch is that which goes to the modulator. The line on 240Ds is teed into right at the group on the valve cover. Follow the line up from the trans.
Basically it needs to be high at idle and proportionately reduced by throttle movement untill gone at full throttle. For an indepth discussion of these systems see the article I wrote. There are a lot of variations but the concepts of control are discussed:
http://www.continentalimports.com/ser_ic20242.html