It is the second most restrictive piece of the exhaust after the POS crush flange in the Y-pipe.
The cat is actually 2.5" in/out (on 2.25" pipe) with a very decent frontal area on the honeycomb. It's not much of a flow restriction.
I have seen flow bench tests of cats before and placing honeycomb in front of gas flow is a very large restriction. So much so that is should easily rival a resonator no matter how restrictive it may be.
Originally posted by DemonSVT: Your thinking about "needing" back pressure is incorrect. An ideal exhaust would have minimal to no back pressure and the highest exhaust velocity while sustaining enough volume to achieve maximum power.
You DO NOT want back pressure. It's part of the trade off to achieve velocity (piping size) and volume control (mufflers)
I did NOT say back pressure was needed. You must have misunderstood.
