I'm Stumped!! Exhaust fighting

[j.fro]

You are correct that the exhaust "runs into itself". I've got a feeling that this is a major part of what cancels out the resonance that the motor naturally produces, which is why many of the after market mufflers have lots of drone.
The muffler has five chambers: two outter, two intermediate, and a center.
Gasses come in on one side and go into the intermediate chamber through perforations in the pipe. Then they flow to the outter chamber on the opposite side. Finally, they flow through the center and out.
The internal muffler mod:
On the central pipe coming into the radiator, use a dremmel or other tool to cut open the pipe allowing gasses to flow directly into the outter chambers. The sound is nice, and there's not too much resonance. The more you cut, the more sound you get.