OK, so this vacuum unit has 2 pipe connections, and there's a pipe which is on the top of the carb, manifold-side of the butterfly, and another pipe attached to a stub on the manifold. The latter sucks quite a lot all the time, the former less so, but might do under other conditions than I've looked at it.
on the vacuum unit, one connection faces away from the distributor like the type with only 1 pipe, the other is on the "back" of the unit.
which f***er goes where?
Haynes, predictably, offers no clue on the subject.