yeldogt,
i traced the vacuum leak to the center vent actuator. so i plugged that vacuum feed line. which stopped my vacuum loss and allowed the rest of the system to work properly.
for the center vent flap, when i applied vacuum there was no resistance at all so the center flaps did not budge. the only part of the actuator that i could see is the little nipple that the vacuum line attaches too. that little nipple to the center vent actuator moves around so i think the whole diaphragm is loose. i poked a screw driver thru one of the vent opennings and manually openned the center vent flaps - they stayed open. . how is someone supposed to get at that actuator inside the heater box!!!?? was the whole car built around that little thing?