1973 Mark IV Vacuum Lines

Greetings from Denmark.
I have a 1973 Lincoln Mark IV. I am writing to you because I am looking for information about the vacuum hoses which runs to the distributor. Please see the photo. What is this (red arrow)? I am hoping you can tell me how this system works, and how I can examine whether it works as it should.
Sincerely,
Ben
—————————————————————————————————————-
Greetings Ben –
Because of the multitude of factory running changes to the routing of vacuum lines and revision of controls and switches in the engine management and control systems during the production to many 70’s vehicles I cannot begin to correctly explain the operation of these systems in your particular 1973 Mark IV. Anyone trying to do so would need the actual vehicle on site along with all of the Factory Shop Manuals and booklets that were available to the Dealers during that era of cars. You would then need to study the information in these manuals and read up on how they operate in order to diagnose problems or perform certain tune up procedures. We may be able to help you obtain some of these manuals if you do not already have them.
Sincerely,
Bill