The sales man told me that the Utlra-Flo series are LOUD.  They are straight through pipes.  We talked about an hour or so, where I described what I wanted and did not want and he recommended the Super Turbo muffler.  I like the sound from the muffler and monza tip.  Out side you hear it, not too loud but a nice throaty sound.  Inside it is quiet.  You hear it slightly on deceleration, but at 5000 rpms it is quiet inside.

Too much backpressure hampers high end power AND NOT enough backpressure hampers LOW END power.  You have to have balance in the muffler.  Kinda like Goldilocks: IT MUST BE JUST RIGHT...

Robert