Originally Posted by 03Z33

What the video doesn't show is the different settings, it's spring loaded and clicks so you can go from fully closed to fully open or stop at a few points in between so:

0% (fully closed)
30% (first click)
50% (second click)
80% (third click
100% (fully released)

These are rough numbers just to help you visualize it. Each click the sound gets progressively louder and power/flow are barely affected at all but the fully closed position. You won't be driving around at fully closed very often unless you're just cruising slow around town/neighborhood and need to be super stealth. I recommend opening it at least one click for any higher speed driving which is still significantly quieter than fully open.