[1LE Red Dragon]

I also used to work for an OEM exhaust manufacturer in Toledo Ohio. Typically, the OEM and aftermarket replacement systems are not designed for power, they are designed for sound. Different baffling arrangement, resonator etc are used in OEM to get desired sound. If a crushed pipe has no affect on airflow, then the laws of fluid dynamics that have existed for many years, are all bogus. This is not the case. The velocity of the air will increase as the area is decreased through the crush section, and the flow rate stay the same. This will cause increased back pressure. This is fact.

Q=V*Area. If Area goes down, then Velocity, V must go up to keep Q (flow) the same. Increased velocity through this crush section and additional frictional losses.

If this were not the case, then no mandrel bent exhaust system or straight thru muffler would ever have added horsepower or torque. This is also not the case. NA motors are not as sensitive to back pressure issues as a turbo or supercharged car. Turbo being the most sensitive to back pressure because of the backpressure in the turbine housing which has a very small area.

Put both setups on a flow bench and you will see a higher air flow rate through the smooth diameter pipe compared to the crush diameter pipe. However if the crushed sections air flow rate when run on the car is still capable of flowing the amount of air needed for the airflow being moved by the engine, then the HP increase will be insignificant. But make no doubt the air flow potential of the fully circular area is greater than the crushed pipe and its reduced area.