Not sure if this is old news. But came across it when looking for a few things...
An Exhaust System designed with two types of gas paths. Switchable at the flick of a buttom.
Kreissieg F1 Race exhaust system is a unique design that delivers performance and sound on demand.
Unlike any other exhaust, this system allows the driver complete control over the exhausts performance and sound attributes.
Normal Mode: This path is a traditional path that takes the exhaust through the catalytic converters and muffler chamber before it exits at the rear tips.
F1 Mode : This path bypasses both the catalytic converters* and muffler chamber, thus taking the exhaust straight from the manifold to its exit at the rear tips.
F1 Mode produces the greatest possible horsepower gain with a true F1 race-style sound.
Strategic placement of butterfly valves in the system allows for instantaneous control between Normal and F1 modes.
A switch placed within the cabin controls the valves. With a simple flip of the switch, the driver selects between Normal and F1 modes.
LINK:
http://www.kreissieg-usa.com/?_page=...dx=1661&page=1