I have a 2000 5.3 Silverado Z71. I am looking to install dual exhaust. What is the preference, real dual exhaust or a cat back system? Would I need high flow cats? What size 3in or 4in stainless? What muffler has a good sound but not overpowering in the cab and would still like to have the sound not go away at 60-70mph. Looking for any other performance mods for towing a 28ft enclosed trailer.

Your truck has dual cats. You could replace the cats if you want, but for your money, a cat-back system would work just as well. I have one 3" muffler (dual in, dual out). I'm not sure exactly what brand it is, previous owner installed it, but it is loud, and sounds great. You don't want to go any bigger than 3" otherwise you will lose backpressure, and engine will not run as well.

Also look into a K&N FIPK system to help your tuck breathe easier, and maybe a custom tune might help with towing.

Yeah like rjeffery said, dont go to large on the pipes, and If your going to do light bolt ons you dont have to worry about replacing the cats

I have a magnaflow dual in/dual out 2.5'' and it sounds awsome, perfect for me, I dont want to wake the neighborhood when im in it, yet its not loud inside the cab, and like you said at 60-70 with the windows down you cant hear it, but if I get the rpms up around 4.5k k at highway speeds it sounds nice, i love my magnaflow.

http://s41.photobucket.com/albums/e261/knogoodidleft/?action=view&current=outside.flv
thats a video of my exhuast, first rev is a little over 2k, the second is 4k

as for towing, a tune would make the most difference.

The stock cats on our trucks flow good. No need to do true duals or 3" pipes unless you have 500+ horsepower. The stock 2.5 inch tubing works well. If you want duals just get a single in/dual out muffler. I think just a straight through muffler like magnaflow or borla dumped sounds and looks best.

for towing a 28 foot trailer, you'll need backpressure for torque. so i would say no to a straight through muffler.

I had a local shop put duals in on mine, just straight pipes back from the cats. That lasted for about two days; couldn't stand the sound, lost tons of back pressure, and probably lost about 2-3mpg. I picked up a Flowmaster 50series Bigblock 2 in/2out muffler and definitly love it. Very low cab noise all together and it seems to dissappear around 60, I also gained a little low end torque, 4mpg, and the motor seems to run a little cooler when towing.
Heres a couple clips of the exhaust
http://www.youtube.com/watch?v=wRUKFtdNRn0

http://www.youtube.com/watch?v=fLLC1SPy57I

Also I tow a 24ft enclosed and it pulls like a dream, All I have installed is a FIPK and the exhaust but the 6.0L and a 4:10 probably helps a little bit.

I had a local shop put duals in on mine, just straight pipes back from the cats. That lasted for about two days; couldn't stand the sound, lost tons of back pressure, and probably lost about 2-3mpg. I picked up a Flowmaster 50series Bigblock 2 in/2out muffler and definitly love it. Very low cab noise all together and it seems to dissappear around 60, I also gained a little low end torque, 4mpg, and the motor seems to run a little cooler when towing.
Heres a couple clips of the exhaust
http://www.youtube.com/watch?v=wRUKFtdNRn0

http://www.youtube.com/watch?v=fLLC1SPy57I

Also I tow a 24ft enclosed and it pulls like a dream, All I have installed is a FIPK and the exhaust but the 6.0L and a 4:10 probably helps a little bit.

Just out of curiosity, why are your rpm's that high at 70mph? Is it because of your 4:10 gear ratio?

I purchased the Magnaflow Single in dual out Cat back system and installed it in my garage. On first fireup it sounded great. However, when driving from 1000 rpm to 2000 RPM it was like being in an airplane in the cab. You couldn't hear yourself for the noise. It didn't get better at highway speed either.

I took it to the local muffler shop and they said this was their 5th one this month they had to modify. What they do is install a resonator between the Catback and the exhaust. Which if you look at Flowmasters Single in Dual out system it comes with anyways.

Upon phoning Maganflow they said that they DID NOT Warranty against noise but, would honour lifetime warranty on the muffler. I hope to hell I own this thing long enough to get a new muffler out of these guys. My Pipes go straight out the back and even with the Resonator I get 2 + MPG and I love the look and sound.

Final Thought:
Go with the FlowMaster series or Borla series...

-Evan

Just out of curiosity, why are your rpm's that high at 70mph? Is it because of your 4:10 gear ratio?

Yeah the 4:10 ratio really runs the rpms quite a bit higher versus the 3:73 I had in my old silverdao, really hurts at the pump too..buy most people don't by trucks for the mileage right? haha

i had straight pipes on my 2000 5.3l. now i have a flowmaster original 40. neither sounds that loud to me. i dont understand why everyone here thinks so. i even thought about removing the cats, just to make it LOUD ENOUGH. and i even put shorty headers on, trying to make a difference. but i am still unsaticefied.

i have a '03 silverado w/ a 4.3 v6. i got a flowmaster 40 series installed several months ago.

single in/ dual 2.5" out

exits behind the rear tires

its louder than my friends '97 4.8L f-150 with gibson exhaust

The best exhaust I had that was very nice, was when I removed the muffler and replace it with a y-pipe then dual pipes out the back.. Had a very nice sounds comming out the back and did not resoniate into the cab.
At idle it had a nice low rumble, but when you got the RPM's high, it would really roar. At highway speeds you could hear it but would not give you a head ache.

Now I have a single 4" pipe comming out the side before the rear tire. Sounds really good and louder, but now I have the resoniating sound in the cab.

Hey guys, I just bought and installed a Flowmaster Cat Back Dual system with the 50 series . Sounds and runs awesome now. I had a few response about getting a custom tune in the above posts. Where or How would I be able to get one of this done.

Hey guys, I just bought and installed a Flowmaster Cat Back Dual system with the 50 series . Sounds and runs awesome now. I had a few response about getting a custom tune in the above posts. Where or How would I be able to get one of this done.

http://www.nelsonperformance.com/

reading all of those nelson testimonies almost had me. would it be that big of a gain for me?
2000 5.3 z71 singlecab/shortbed
edlebrock shortys & flowmaster fortys....
(k&n air filter too)...
how much power gain might i see perhalps?

I cut out the old muffler and installed a Borla Turbo muffler and left the tailpipe in the stock position. The tailpipe had a problem so I cut it off close to the muffler and installed a short pipe with a 90 degree bend to it and installed a duel tip just ahead of the rear tire. Not only did it look better but it sounded the way I wanted it to in the first place. This was on a 2000 5.3 like yours but not a Z71.
http://www.hunt101.com/data/500/PA170040.JPG

yes, but i think borla is too expensive to be just a straight-through muffler. (what's the point?) i'd just go straight pipes before i'd spend that. but back to that nelson tune...

I paid $150 for the Borla and my previous truck had a straight thru exhaust and I'll never do that again...it was way to loud.
Plus in another post in this thread didn't you say:
for towing a 28 foot trailer, you'll need backpressure for torque. so i would say no to a straight through muffler.
I agree with you on that one...I towed a gooseneck two horse trailer and with the K&N FIPK and a SuperChips programmer the truck was way better then stock.

i was not dissagreeing with myself... i just said that borla was no better than straight pipes when it comes to horsepower/torque. yes, i still think you need backpressure for towing. and i'd recommend a 50 series flowmaster for that...

I think I understand now...with or without the Borla you get the same results...just not as loud.

hey Mod 12.....when u installed your flowmaster catback system, is it the dual rear exit system(under bumper), and if so, did it clear the spare tire & hitch????---thanx for any help.....

http://www.nelsonperformance.com/

I did some research before i got mine and from what i've found it seems that Nelson's company got way too big for him to handle so now his customer service and tunes are lacking. I went with a Blackbear tune from Justin. He makes a great tune and gives quick customer service. He also teaches EFIlive university so he knows what he does. I think his prices are quite a bit cheaper too www.blackbearperformance.com