It has been awhile since I posted, mid-winter lethargy.
I replaced all the vacuum lines with bulk lines from Porsche. They kept slipping out of the rubber elbows and "Y"s if I so much as touched them, so I ended up putting spring clips on them.
I checked that all the valves and other elements of the system worked but there was still a vacuum leak which I traced to the vacuum reservoir. I used my homemade can of compressed air to test the reservoir after getting it wet and found the leak in the bottom at the edge. The blue arrow indicates the positioning pin that goes in the mount and the red one where the leak is.
I have a second used reservoir and it had a leak in the same place vis-a-vis the pin.
I wonder if vibration passed through the mount causes it to crack here.
I think I will reseal them instead of buying a new one.
The snow is almost starting to melt so I have been shovelling it from around the Boxsters to be ready to get them mobile when snow tire season ends in less than a week. Yay!