Catalytic Converter Replacement Needed

rngr746 · September 8, 2017

My truck is an 07 GMC Sierra Classic with the 4.3L engine. I have shorty headers and a cat back exhaust system. I need to replace a bad cat and have been told it would be advantageous to replace them both. I am thinking about going with high flow/performance cats. I am seeking members recommendations, experiences, and advantages (good and bad) about high flow /performance cats.

Supreme Pizza · September 9, 2017

Is emissions testing required in your area?

rngr746 · September 9, 2017

Emission testing is currently required but due to be eliminated in a year or two. I shouldn't need to get the testing done in the future.

Supreme Pizza · September 10, 2017

One option would be to remove both cats, and just replace them with a strait piece of pipe. If there is no need for emissions testing, then you should be able to get by without them. Might even get better exhaust flow. The down stream sensors will throw codes that say something like this: "Yo, your cats ain't working so good". I would recommend verifying that this procedure will work on your rig before trying it, and its probably not technically "legal" to remove them. Maybe check google for the results of others for instance. Every vehicle is different, but I know that many people remove the cats when they upgrade to better flowing exhaust systems. I have run over my own cats when they fell off, and the rig got louder, but it still ran the same. The purpose of that part is to lower the exhaust emissions by super heating the exhaust before it is expelled. Aside from the emissions, it doesn't do much (the the best of my knowledge). Maybe some exhaust guy might know more on this.