Ok, I've read the recent posts and Vanagon.com FAQs and the archives.
 My 2 questions re my 1991 syncro are:

1)  My diff-lock servo unit (on tranny) was taken off by the PO as the
    plunger into the tranny had broken off the servo unit.  The 'plunger'
    into the tranny seems to work OK as does the servo unit.  Is it
    possible to hook up a manual (choke like) cable to the diff-lock
    unit ??

  2)  What is the advantage of a vacuum activated diff-lock switch?

3)  the diff-lock vacuum bottles lines (or Y connectors) were making a
    whining noise so I have blocked them off with golf tees.  Am I
    doing any harm?  Please keep in mind that I'm running carbs not FI
    on my '91 syncro.

  Thanks,Malcolm S