I am happy to report that I tracked down the vacuum leak to the passenger's side main air flap actuator (double element # 44). My local dealer had the part for $110 while George Murphy sells them for approx. $45 - can't beat this deal.

Only in the end did I realize I was going about it backwards. I started tracking the vacuum leak at the lines, something that took me hours to do, when instead I should have started at the weaker diaphragms of the actuators, these I could have tested in minutes and ruled out first.

All in all, I had a great time working on my car and take pride in doing the work myself. My mentors Richard W. and George M. were so nice to answer my questions, I just hope I can help someone out and give back to the MB karmic account

Regards.

Max.