http://tonemonday.com/accessories.htm

Look towards the bottom under "Perfomance" there's a listing for Powervault Muffler.

There seems to be very little benifit to having a dual muffler system with the VX under it's current engine/drivetrain configuration. It's mostly a "looks" kind of thing. That being said, I believe there a few on the list who have used two Powervaults to achieve this "look."

-- John