Hello Tina,
This is an important question properly asked. Finding your level of understanding is what is causing the confusion.
In my opinion, a vacuum advance is there to advance the ignition at hi vacume, low throttle opening, for better fuel milage. It usualy advances the timing well past best power. In an aircraft not much time is spent at low power, high vacuum, so there is not much value in the device.
Tim is trying to show you how to work around the timing issue because the factory timing is set with the vacuum advancing the timing.
The hose should be pluged on the manifold end as it acts as a leak in the intake system and will often cause low speed mixture problems.
Please keep asking your good questions and pushing back when you don't understand the answers you recieve. You are never the only one with the question and often the knoledge base gets cleaned up when the answer is more basic.
You have one of the most contagous smiles I have ever seen. I look foward to your posts because of it. I also enjoy your enthusiastic approach to things.
Thank you, Vance