Hi David,
I've been chasing down leaks in my vac system and it can be a real PITA! Fortunately for me I was renewing the HG so everything came off which made the job a bit easier...
You've probably already seen them, but the diagrams on the Lindsey site are really helpful and any other photo based diagrams I found on the web weren't that much help tbh.
http://www.lindseyracing.com/LR/Parts/VACDIA.htmlThe first job is to whip the inlet manifold off as everything will become much clearer then. It's useful to have the diagrams available next to you (I brought them up on an iPad) and then traced everything. On the later 951 the system is actually a lot more simple than on the early car, so I've now reconfigured mine as per the late set up.
As you're running a DPW the cycling valve system should have already been junked, but you'll need the manifold off to get to it properly. I've removed the lot on mine as it was all knackered any way and like you I'm running a DPW.
It seems like a massive birds nest at first but once you've got your head around it all it's not so bad! Most of the hoses are still available from Porsche.
Have fun!