Sorry I don't but, I am experiencing a low vacuum problem myself now and I think I stumbled on the root-the main vacuum tree.
The vacuum tube to the SC bypass valve, return plenum, the hose on the rear of the intake plenum and the windsheild wiper hose all connect to the main vacuum tree. Follow anyone of those lines to it near the drivers side firewall.
You might just need to cut some new rubber to seal on the vacuum tree or up plug each vacuum line and plug one end with your finger and suck on the other end to see of you have a leak.
I hope this helped. Good luck.
Metalman