If backpressure along helps low end torque, then a simple dyno test would prove this by adding a simple restriction to the end of a large diameter exhaust system.
The Supertrapp muffler is an appearly simple but sophisticated tuned engineered muffler system. Note that in the link below Supertrapp mentions that the disc are tapered, and that others had tried to copy their design without success. Revealing all their design principles would not be beneficial to Supertrapp.
http://www.supertrapp.com/resource/faqs.asp I have used the Supertrapp muffler before on a SCCA sports road racing car, but due to the rules we were not allowed to tune the exhaust from the one provided.
Are they any articles with dyno tests of the Chevrolet straight sixes, like you see so many of the V-8's?
