It looks like a controlled resonating vacuum leak. I could see how a tuned intake resonance could be beneficial but sourced from a vacuum leak could be bad. Especially on newer computer controlled cars that account for every bit of air going thru them. Someone should try it and see .
Best tank= 81.23 mpg on july 1st 2008
SAVE SOME GAS, SAVE THE WORLD!
Sorry, BOV = Blow Off Valve. On Turbo charged engines its a valve that reroutes boost when you let off the gas. Its the source of that psssst sound when someone shifts
From its description that what it sounded like to me, a device that vents manifold vacuum when you let off the gas. I was just wondering whether or not there is any credibility to the functionality of such a device.