After getting under my truck for the first time to replace rear shocks I noticed it has three mufflers along with the cat converter. No wonder my truck is such a slug! Who makes a good cat back system that is not overly loud and wont break the bank? Truck is a 2006 3.7L

 

The real reason that it is "such a slug" is that it is a big heavy vehicle with a 13-year-old Chrysler V6, which is at least 20-year-old technology, and likely older than that.

It isn't a little hondoo civic with screaming 4-banger. These aren't meant for the drag strip out of the box. It will pull stumps, however.

 

That’s one muffler and two resonators which are just big hollow tubes. Any cat back system will work. Just depends on how much you want to spend. Remove everything after the Y and install the exhaust of your choice. Be aware, the major source of restriction in the exhaust is the Y pipe. They used to make an aftermarket replacement. Not sure if they still do.

 

Aluminum Cat back systems will run around $300, and Stainless steel will run around $600+. Good brands (Opinions on sound will vary greatly) with systems for our trucks are Magnaflow, MBRP, Flowmaster, Borla, and Gibson. Exhausts will be either single or dual exit, side exits, angled exit, or straight out of the back. Aluminum will obviously not last as long as Stainless Steel, and T304 Stainless steel systems are better than T409 Stainless steel.

I have the T304 Borla single system, and this system will outlive my truck for sure. Oh, and it sounds amazing.
(V8 and V6 sound waaaayyyyyy different though.)