Yes an aerospace vacuum pump system, and that's another question since I have not had experience with a vac system.
Can that impact this oil on plugs at all?
Does the tank need to emptied periodically or maintained in any way?
I know they had replaced bearings and "rebuilt" it just before I picked it up because it had a slight tick, which I thought sounded like a lifter but it was gone after they "rebuilt it"
Pan Vac is a great indication of the engine health. Yes you should monitor the pan vac during a pass (data log) as this tell you if the engine is happy with the tune up ( timing/AFR)
Yes you should empty the catch can after every pass and monitor that, its literally a dynamic leakdown test of the rings as the engine is running ( as long as there are no other leaks letting air into the engine)
IF you have a stuck ring or nipped piston, the catch can will be getting a LOT of oil in it with the engine running....
