[fastd]

My understanding of optimizing exhaust performance: the focus should not be so much back pressure as on velocity.

The wider the diameter the pipe, the lower the velocity; low velocity is generally not a good thing. So in order to make the "best" diameter decision depends whether you want focus on lower rpm power or upper rpm power. Does that sound right?

Can you all share your observations with respect to exhaust performance, especially if you changed from a smaller diameter to a larger diameter, or changed muffllers from restrictive to less restrictive? What did you have before, what did you change it to, what dyno hp and torque did you pick up, did you notice a "seat of the pants" power reduction at low rpms...anything else?