Originally Posted by -PEPE-

To the OP, That is NOT a resonator as suggested, it's a non-02 monitored 3rd CAT add by GM for CAFE compliance, it was GMs easy/quick response to CAFE.

Several have gutted these 3rd cats from 09-13 and shared this information on several forums.

You're going to get a ton of taste variations in a thread like this, it's all about personal preference. Based on what you stated thus far I'd offer the suggestion of Borla S-Type pn# 140429. This was designed for "our" trucks specifically tuned for borla's deep throaty sound. The S-Type only comes in dual split @bumper and NOT in the rear-wheel split, that only comes in the Touring. You can also get the Touring in the rear bumper split but I like the louder better tuned new version. The tips are brawny and have a huge O.D. which appear larger than the typical 18" chrome redneck tips some call them. No offense to any rednecks, I used to use them too

Autoanything sells this catback for less than anybody else with free shipping.

You could elect or not to gut the 3rd which will NOT throw any codes since it's non monitored. It really doesn't give you anything worth mentioning powerwise, but a slight sound difference is all. Gutting only, leaves the shell and passes visual for inspection/warranty. GM Service doesn't go around x-raying our CATs. They can inspect that's it is there though and void warranty if missing. Many offroad pipe the 3rd cat, but it's up to you, I like my warranty for now.

Have the same truck basically, 4x4 crew cab 5.3L and had my borla for 2 days now, but there are other great systems out there. I've had Borla on a couple of 5th gen fbody's until I outgrew them needing dumps for the stroker. You'll love the borla I guarantee it.

I'm making a sound clip hopefully this evening and will share it if that helps.