I've got the Magnaflow 12589 on my 05 ECSB 5.3 2wd Silverado. It is quiet as stock while cruising (below 60mph), slightly audible while cruising above 60mph, and sounds mean on WOT. It should be a noticeable improvement over what you have.

 

I got 2 of those, LT's & gutted cats straight out the back...its pretty loud...if I keep the truck, I'm gonna quiet it down...got pulled over by the local po-po and they tried to give me grief...cudnt believe I'd just passed emmissions so there wasnt much they cud do with out a DB meter.

 

Have the high flow cats from ARH.

 

More cyl press, exhaust velocity, basically alot more **** crapping out the pipes

 

x3 on the 22'' case magnaflow. nice and quiet but has some bark when you open it up.

 

That's idle. Let's hear it! Throw some revs at her!

Thanks John.

 

i heard a gibson today on a 5.3 not sure how big it was but it was damn near silent till wot, and even then it wasnt very loud

 

heres a 30" but im not sure if it would be loud due to being round
http://www.magnaflow.com/02product/s...e=main&id=8421

 

called magnaflow,and was told that 12579
http://www.magnaflow.com/02product/d...rtnumber=12579

is the quietest they have (Same one corey/blackgmc just got )

and if its still too loud to put 12619 before it

http://www.magnaflow.com/02product/d...rtnumber=12619

 

I have a pair of the 12589's as well and find them very loud going from a Corsa touring which was basically only really loud at WOT. The 12579's look like the same muffler other than no offset.