[Maser077]

I don't want to mislead you here, and its very hard to diagnose these things without running a few tests. However, I'm not so sure this is related to a vacuum issue or pressure issue. I suspect pulling the dip stick and having the pressure drop is simply impacting something else, unrelated to the vacuum and pressure. Listening to the video, you can hear a distinct sound as the revolution progresses, pulsating as the cylinders fire. I bet if you put a load on the engine, the sound fades away and comes back as it returns to idle. Sorry, I can't help more than that without running tests.