Probably the biggest potential for leaks on the '80 is the climate control II system. If the heater/AC works, it must not be leaking, but if it doesn't work properly, one can categorically state that there are vacuum leaks, most likely bad vacuum pods. Cycle the controls, see if all the air comes from the defrost vents (indicating bad pods elsewhere), if any air comes from the footwell vents (if not, bad footwell pod), if any comes from the AC vents, etc... Another potential leak area in the climate control II system is the servo area. There's a real ratsnest of tubing there. If the AC and/or fan doesn't come on, it's usually a leak that causes the vacuum switch not to operate to turn on the unit.

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C