The video sounded like an air leak whistle to me but could easily be mechanical. Might be easier to tell if the RPM were varied while filming. I had a leak that sounded like that when I worked on the intake of my G35 and didn't get the gasket surfaces sealed right when reassembling. A bigger leak like a broken vacuum line usually sounds like a hiss but a small leak between two flat surfaces can make a whistle sound.
To test this hypothesis, you could introduce a huge air leak to reduce the vacuum on the intake. If your sound remains unchanged, it's probably not a vacuum leak. But if you pulled the PCV hose or some other big vacuum line and the whistle goes away, I would think that points to a vacuum leak because now whatever surfaces are drawing in air will not be the low pressure spot and that small leak will probably stop altogether. You'll probably set some kind of code doing this but you can reset them with an obd reader or battery disconnect. This wouldn't tell you where the leak is. It would only help you narrow down if you have an air leak or not.
