Hi Mike- have been watching your follow ups with interest.
 I was thinking about you vacuum at idle. I never rebuilt a VW- but i have
rebuilt some Chevys. Here is my experience,i also had some vacuum issues.
 I had a 72 Monte Carlo with a 350 ci engine. Motor ran good, but i wanted
more power.  BIGGER CAM TIME!!
 I thought that this would boost power a lot. Before i put the cam in i had
16 inches vacuum at idle. I put in a big cam- more lift and much longer
duration. Idle vacuum plummeted to 10 inches at idle. Had to do all kinds of
rejetting to get the car to run right. Major PIA!
 Contacted the cam manufaturer  (crane cams- very reputible)
They told me that as cam duration increase, the vacuum will drop at idle.
This is due to lower cylinder pressures at lower rpm.
 I dont know if this helps you, but it might shed some light on the subject.
Brian
83 Urabus

Ps my solution was to install a set of variable duration lifters- Rhodes
brand.
This boosted vacuum up to 12 inches, and made the car much more drivable.