Post by
nametakennow »
https://forums.nicoclub.com/nametakennow-u713.html
Mon May 18, 2009 1:39 am
The high flow cat is a replacement for the cat in the middle of the system. Make sure to move your 2nd O2 sensor behind the high-flow or one of the other tricks to make sure you don't throw a code (the full list is in the Common Fixes thread in the Table of Contents).
Sound won't be an issue as long as you have a proper catback exhaust. Even the stock one is better (sound-wise, though flow is an issue) than a cheap muffler. Make sure you have a resonator as well (again, stock has one, but the stock piping is smaller than your header's midpipe, so it's recommended that you get an aftermarket catback to go with the header).