Ian et all,
You may be thinking of a spiral muffler. The concept is patented, but both Jegs and others sell them as race mufflers. Our dyno testing shows negligable hp loss. That being said, you still need a muffler with volume. To be really quiet, you need a muffler with a street rating, not a race rating. We have to run under 93 db wide open throttle at 50 ft.
Wayne