Exhaust gases cool as they travel down the pipe, so its been found that mounting the mufflers as far rearward in the chassis causes two benefits: Less heating of the mufflers, and since the exhaust gas is a little cooler, the size of the tailpipes is less critical. A larger case (size) muffler usually deadens sound and flows better on a given application.
The placement of mufflers, pipe size, and system configuration (H-pipe, X-pipe, Y-pipe) all depends on engine & header parameters, the purpose of which is to achive the elusive "tuned" exhaust.
As far as just 'sound' I'm curious how muffler placement afffects it. It just depends, as the obtaining of the resonant frequency of engine exhaust in its powerband depends on distance of mufflers from collectors. Prolly the presence of tailpipes quiets any system down from there.
Thats my SWAG anyway.
Chip
