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Discussion Starter #1
Newb needs some input. Got a 2001 Sierra 5.3, hypertech, and cold air intake. I have been puttin off getting an exhaust because I don't really want anything louder than stock for hunting and long road trips. My buddy suggested getting a few more ponies and mpg by doing something with the cats. First thing he suggestesd was cutting them out completely (which yes, I know is illegal), another buddy said open up the existing ones and just hollow them out (probably illegal too), and the third said go with some aftermarket universal fit magnaflows (but I hear there is no real gain from these and they burn out quick). All three ideas intrigue me, but I don't know enough to make the best decision. Again, I'm looking for mpg's and more ponies for driving through the mountains.

BTW,just how constrictive are the stock cats?
 

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The stock cats aren't that restrictive. Don't take off the cats your truck will be super loud. Don't try and hollow them out you'll probly just end up having to replace them. The maggies are a good idea if your going all out on exhaust but just as direct replacement you wont notice a difference in power or MPG. I added a magnaflow muffler and love the sound. It's nice and deep when at WOT but at crusing speeds is completly silent. Unless you plan on doing a full exhaust system don't get your expectations to high on performance.
 

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Yea, messing with the cats wont change anything if you arent switching out the exhaust first. Once you upgrade exhaust, the magnas will help free up a little, but not anything major, maybe 2-3 horses.
 

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Discussion Starter #4
Thanks for the info. The question ended up answering itself...I took the truck into a trustworthy muffler shop and it turns out one of the cats was plugged pretty good and the other wasn't much better. To top it off the stock muffler was leaking at the welds so....it's getting two new magna cats and an imco muffler (I hunt a lot so I wanted something as close to stock noise levels as possible) this afternoon.
 

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Thanks for the info. The question ended up answering itself...I took the truck into a trustworthy muffler shop and it turns out one of the cats was plugged pretty good and the other wasn't much better. To top it off the stock muffler was leaking at the welds so....it's getting two new magna cats and an imco muffler (I hunt a lot so I wanted something as close to stock noise levels as possible) this afternoon.

Good for you in keeping the CATS. Let us know how it sounds compared to stock.
 

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Discussion Starter #6
It sounds pretty darn good to me. It's slightly louder than stock (barely) but lower toned (the stock had a whine to it). Power gain is not huge but it is noticable.....seems like I lost some torque though, I'll pull my battery to reset the comp and give it some time to adjust.

You know...come to think of it, it sounds like my stock 86 Chevy 3/4 ton 350 used to....you know, when stock trucks sounded like trucks.
 
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