Ok so ive got this 01 Regal GS now, and one of the things im most happy with is how comfy and quiet it is. So the SLP intake didnt make the intake that much louder (no where near what an intake does on an M62 like in the Bonne) and it still had the stock exhaust. So what im thinking is an Intense high flow cat and right behind it a Flowtech race ready cutout with a DMH Performance electric cutout controller (http://www.dmhperformance.com/) But what I want is to still keep full use of my stock O2 sensor....so what im wondering is will this all still work if I have my exhaust man weld in a bung (no jokes here!) to install the O2 sensor in a small place behind the cat. Right now the Buick has this U Bend (notorious power robber) thing right behind the cat that has the O2 sensor in it. What im worried about is will the O2 sensor be getting any funny reading being the Cutout will be so close to it and when opened it will be flowing WAY more and also exposed closer to the elements. So what does everyone think...I think if this works it will be the perfect solution to quiet when I want it LOUD when I need it......as I would be keeping the stock exhaust from the cat back.

dont they recommend the rear 02 sensor eliminator for the slp high flow cat? i would check into that first.

The rear O2 spoof will work, the O2 sensor does nothing for performance but the spoof will keep the pcm from throwing a 'ses' light. Once you open that exhaust bypass the rear O2 sensor will not get enough heat and throw a code.