Installed newly purchased used Harley muffler on my C5 yesterday and the results from a short ride are promising. A much better sound ( not too loud ) but much crisper and increases nicely with increased throttle. I think the bike is more responsive and seems to have a little higher cruising speed. I used a non-cat. sportster muffler and drilled several holes thru the internal plate so there is slight back pressure but is straight thru design. Total cost $25