[scottj]

Deano- Contrary to popular myth backpressure, which is a resistance to exhaust flow, decreases exhaust gas velocity and does not increase torque. Primary, secondary, collector, and exhaust pipe diameters and lengths combine to affect the velocity of the exhaust within the system. Generally, the reason a 3” exhaust pipe will produce more torque at a lower rpm than a 3-1/2” pipe is because optimal exhaust velocity will occur at a lower rpm. Low rpm = less exhaust gas volume(quantity), so pipe diameters need to be smaller to maintain velocity. Higher rpm=greater gas volume, therefore larger pipes produce optimal velocity.
I run a 3” or a 3-1/2” perforated core straight thru muffler …and earplugs with either.
Scott