I was just looking at the Muscle pipe by Curtis Youngblood. haven't treid one yet, but i suspect it would be even better than the TT muffler. It is a tuned pipe which not only gives more power, but tuned pipes tend to act like a governor to keep the head speed coonstant. Might be worth a look. i plan on getting one for my OS 50 next month.
www.curtisyoungblood.com