Acoustic Valve connects to the airfeed that comes out the side of the airbox near the battery, follow it down.
you can see it when you take off the passanger wheel and then the wheel well cover, it runs a vacumn line to the throttle body.
essentailly it opens and closes to give 1 feed to the airbox at lower revs and a second, colder airfeed to the box and higher revs, throttle....
sounds a bit beefier removed as well.
im sure someone on here can help you out