So far I am seeing that Turbo back application in my simulation program to have a better pull in the beginning RPMs, drops off at mid RPM, and does alright at high RPM. Whilst a cat back application with proper pipe sizing back can achieve -5hp and -4 torque at the wheel while providing better high and mid RPM and higher gear advantages. that small 5hp and 4 torque is what I am trying to have a cat back system achieve as well. So a user could have the power of turbo back with a cat back just at different bands. The larger piping and resonator / muffler addition is like adding a flare, although its a large area with some fill, its also a straight through exhaust. Therefor the holes drilled in the exhaust mid section allow for flow into that area as well as the 3" area. It allows for nearly 2x the flow in that particular area.