I have an ‘03 GMC Sierra 1500 4x4 with the small V8 auto. I want to put dual exhaust but hate the catalytic converter that muffles the sound. Can anybody help ke with advice on how to straight pipe my exhast with the cat on or can I delete and be ok? Thanks in asvance! Ken

You can’t remove the catalytic converter without facing fines of up to $10,000 if you are caught. If your state has emissions testing, you will be caught.


Lesson one on ’ How to really annoy your neighbors ’ run straight pipes on your vehicle.


There are “cat back” exhaust systems available to “improve” the sound of your trucks. These attach behind the cat, hence the name. and keep you legal while providing a bit more rumble to your exhaust sound.

Also, if you remove your cat, the check engine light will come on and stay on because the cat is no longer there.

Remember we all like clean air, I do, you do and your kids do. So don’t remove the device that helps us all keep clean air.


I don’t know exactly how the plumbing was but on my BIL’s Fairlane last trip he had put lake pipes on it. Just open the outlet and its a straight pipe. Come to think of it though it would be pre-cat so nothing there. Can’t do that on an 03 though so never mind.

Why is it so important for you to make a lot of noise? It won’t make you faster. Odds are that you have two front cats aka pre-cats or warm up cats. These do not create much, if any back pressure or muffle the sound much. From there you probably go to a single rear cat and then to the muffler.

There is a dual exhaust system that is popular for your vehicle that uses a smaller muffler with dual outlets and dual pipes from there back. It makes a little throaty sound that is not obtrusive, until it starts to rust away, which doesn’t take that long as it is made from some pretty thin metal. But for a little while, it looks and sounds good.

Besides the problems mentioned above, the vehicle won’t pass a state or local emissions test w/the cat removed. Suggest to retain the cat and modify whatever’s beyond the cat, if you want to modify something. If you want a different sound a different camshaft might be available for that engine and still be emissions compliant, and that would modify the sound likely. You’d have to do some googling, maybe surf over to summit racing, to see if anything’s available.

And if the Check Engine Light is always on, how will you know if an engine-destroying malfunction develops? A lot of people hate CELs, and some cover them with black tape, but IMHO that’s foolhearty. A functional CEL can prevent the cost of a new engine by warning you of a serious problem.


back around 2k my friend put a dual cat, dual muff system on his 95’ or so chevy pickup. cost a few bucks. but he was adventurous. than he sold that and got a 99’ or so vortec truck and i think it had dual cats? and he put a dual catback setup on since he didnt really feel like buying 2 new cats. but the generic cats were pretty cheap if i recall.
what is the layout on a 03 truck? it it a dual cat into a single pipe thru a muffler?