Hello Rian,
Thought I would share my experience. I have a QTP Quick Time Performance 3" cutout on my daily driver Camaro. It has been on the car since Dec. of 2005. I have had zero issues with it. I use it all the time. I have it welded in the I pipe just before the muffler. With stock manifolds and cats I leave it open most of the time its about the same noise as a true dual exhaust. My Camaro has the 3" single pipe from the y pipe in front back to the crossflow muffler.
I had it installed professionally due to the exhaust being stainless theres was no way for me to weld the cutout in.
It has a really cool switch that has a light that is red when the cutout is closed and green when it is open.
I bought the cutout and the QTP electric cutout from Summit racing.
http://www.summitracing.com/search/p...xhaust-cutouts
Bret