[Christ]

See, that's why I stopped calling it "vacuum" and started calling it a low-pressure area.

The pressure there is lower than that anywhere else around the vehicle... that said, if the water gauge was calibrated to a high pressure area, such as the windshield cowl, it would immediately show the difference between each area.

I'm not sure what, exactly, the results of the water test would prove, other than (for my car, specifically) how much of a difference there between each end of the vehicle.

And, I don't have a way to video-record the results. I'll probably do it anyway, just for kicks, since that's pretty much why I do everything to my car.