My 06 with 90,00 miles needs an exhaust. The tail pipe and muffler rotted out. Does anybody recommend a CAT back 4 inch system. I don't want anything to loud.

 

I put a MBRP XP 4" cat back in my 04.5.
All stainless so it'll never rot out. Very easy to install.
Very please with it and not loud.

 

I just put a donaldson 51" and a stock tail pipe, works great.

 

Either find a Amazon or EBay deal on a new system for cheap or a local muffler shop that makes their own pipes.
It's already a 4" so no need to upgrade.

 

Just installed a MBRP 4" Stainless XP on my 06 this weekend. Sounds good not to loud.

 

I installed the 4" cat-back Flo-Pro system recently and found it to be very easy to install, looks good and is not loud at all. I have only put about 3500 miles on the truck since the install, but I am very satisfied.

 

I installed an AFE 4" catback about 40k miles ago. I get some drone about 1600-2200rpm when camper is loaded going uphill but some of that may be due to PO gutting the cat. It did not have any catback when I bought it.
Other than that I'm satisfied.

 

Ignore anyone that just tells you the brand they used but not the model. Without knowing what MBRP they used, it's no help. They make 8. Same with Donaldson. Just in the 4" they have quite a few 51" mufflers, and they all flow different amount of air and lower different amount of DB's. It's the same with someone telling you what spark plugs they use in their Dodge... Dodge what? Car? What car? Truck? What motor?
You want quite? If you have a 4", go with a Donaldson M101167 & 30" FTE Res/Muffler.
I started out with the cheapest MBRP system I could find and it was L O U D and had a drone like you wouldn't believe. (amazon was cheapest) Every clamp was tight, every hanger was there. The muffler is about 14" long and is basically a 5" or 6" straight pipe. If that is what you want, go for it. That system was about $250-$300. I then bought the 30" FTE and M101167 Donaldson and... wow. I can actually stop taking so many aspirin, listen to the radio, have a conversation. Before it was impossible. Each one was about another $120 and sooo worth it. The only thing the MBRP muffler was good for was to **** off the little rice burner with the thumping music next to you.
Actually, once you put the MBRP on (that muffler has both hangers welded on) you could actually fit the M101167 in front of it, with the 30" FTE directly after the down pipe and only need about 5" of pipe. Yep, you could run two mufflers and one resonator/muffler if you have a long bed quad cab. Oh, forget those crappy old style bolt type clamps and only use stainless steel band clamps. Makes for easy changes down the road. And yes, I have a mig welder but like the ease of the clamps.
5" systems only have an advantage over about 500 HP. I'm told they sound lower in tone... not sure if that's true with everything else being the same. Many folks say they run the 30" FTE res/muffler in the back just as a muffler and it sounds great. I can't say. I only wanted to do this one more time and didn't want to test, remove, move, test, and repeat. I hate doing things more than once. As for the CAT, most people remove when they can. They do affect the sound/drone. My 03 never had one.
Let me know if you want any links to cheap places to buy the stuff or my list of Donaldson options. Prices seem to very. H*ll, the place I bought the Donaldson from had a price of over $180 over the phone but $120 shipped to me on ebay.
Yes, same exact place.

 

Mine has a Diamond Eye cat back, with muffler. Not too loud but has a nice grumble when you get on it.