The systems holds 10-12hgs...
Cuisinart, I am going through the SAME problems right now... We should definetly talk and share knowledge. I have found several write ups and walkthroughs on how to diagnos and repair/replace every aspect of the secondary vacuum system. I found all the hard to find parts as well. I am to the point where I have the knowledge and tools I need for the job, now I am just waiting for my parts to arrive before I pop the plenum off and get dirty.
Here are a couple of great links I have found for our problem.
http://www.corvetteactioncenter.com/...ad.php?t=14272
http://www.pnwzr1.net/PNWZR1.htm
I got my vacuum hand pump at sears (50$) at tested my lines, I have a leak under the plenum and my pump is burned out...
go to here
http://www.partszoneonline.com/ for your parts needs, checkout my thread "check engine soon" for all the part numbers, also the part numbers are listed in the CAC link i mentioned before... Let me know how you are doing on it and good luck!