'06 Z06 bimodal mufflers

[Musclerodz]

Saw an ad the other day for the new Z06 and they made mention of bimodal mufflers whatever that is. Anyway the text said they are vaccum valve operated so they are quite at idle and loud when you stand on it. In the ad pic you could see the butterfly valves on one side of each exit pipe of the muffler.

Not that I am old but it drove me nuts when I had two chamber Flowmasters on my Camaro and had to turn it off in the drivethru's. Anybody know anything about these or know of an aftermarket variant?

Mike