I am looking to add a 4 inch exhaust and I had a few questions. My truck is pretty much stock except ppe tuner. Im thinking I should go with a cat back because of bs liberal nj emission laws, though their are some ways around them;). Is it worth installing just a cat back exhaust.. Will it lower egt's and help with spooling, or is a turbo back the only way to go. naturally id like to do turbo back but i dont know if the gains are worth the problems of having no cat in nj. secondly im not looking for a loud sound, I just want to lower my egt's and maybe some more responsiveness. thank you in advance.

You will get about 60% of the benefit of a full turbo dp back exhaust. You will see a slight reduction in EGT's, and a small performance gain. The major restriction in the exhaust is the factory muffler, as the cat is of high flow build quality. The Cat just creates heat, which is exactly what it is built to do, so eliminating it reduces heat build up and increases mileage and engine reliability. Figure around 100° reduction with a cat back and a 200° reduction with a turbo back.

Hope that helps,

Chad

Same answer as on DF.com

After dealing with a droning mbrp stainless 4" turbo back I'd recommend keep the cat and get a corsa 4". If you tow any drone is bad news.

If you are worried about the emissions testing etc, get the cat-back kit and the front-pipe (cat delete) separately. This will allow you to swap the cat in and out when you need to. Let me know if I can help with anything.