What should I get for exhaust? I have a 98 GMC Sierra 5.7L TBI. Should I get A catback system or go with true duals? What would I get better performance from?

True duals no cats your choice of mufflers dumped before the rear axle. OR 2 1/2" duals your cats, your choice of muffler 3" out to the back. I run Gibson headers, 3" true duals no cats, Super 40s dumped before the axle. Plenty of bottom end, great top end and I finally got away from the "cackle". Just real deep and real smooth!

If you don't off-road alot, dumping them before the axles is ok. You've got to watch how close they are to the tire or they'll get smashed and ripped off on the trails. Personally, I'd go with true 2 1/2" duals, Dynomax Turbo or Ultra flow Mufflers [not just one for both, but one for each pipe], and split out the rear, no cat[s]. It's a nice smooth deep mellow tone. If you want to run shorty or long tube headers, thats your choice. Right now I've got a set of Pace setter's Shorty headers that I'm running. They seem to be doing pretty good, a little more umph at start/mid-range. Also if you're going to run an exhaust system, run a performance air filter [K&N for example] or an open element. I've had no problem with either, but I seem to get more power with the open element. It's purolator [don't have part number] with a foam wrap, and I used a Holley 2 barrel carb air cleaner housing. All I had to do was drill two new holes in it so it would fit on the factory studs.

I ended up hiding mine... I tore off my rather expensive gibson cat back system climbing hills.


Thank God I was able to fashion up this set of pipes from the peices left over...







Plenty protected from my bad driving now.

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True duals no cats your choice of mufflers

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Don't start messing with your cats if you have to pass emissions....don't know where in Ill. you live but it may be an issue for you....

True, if it must pass emissions leave it in, or if you have A.I.R. injection leave it. I know Michigan doesn't and most people here just rip it off, because they're pretty much useless for performance purposes.

I took the cats off for performance. There aren't any emmission testing in KY. I also installed the O2 sensor simulators in place of thr second set of sensors. Truck runs great.

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There aren't any emmission testing in KY

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I live in KY and have to get mine checked every other year. Just because they aren't doing it (yet) in Russell County doesn't mean it's not already being done in Boone.

Be careful if you remove them, because it's only a matter of time before the lawmakers decide that it's an easy way to raise some $$$ and it's all over.