Sparko makes a good point. Magnaflow mufflers are packed much tighter packed with rockwool and OEM isn't, its just a big 31" muffler. I would still say go for the 18" body, but start with the 24" body. The 5x11 oval case will absorb a heck of alot more volume than the 5x8 version. Being only 2"s longer wont kill down the output volume as much as the 5x11. I would say go for the 5x8x24. A part #12289 muffler is waiting for ya

 

No need to apologize. I miss stuff on here all the time. Just didn't want to bogart Darren's explanation.

 

Update:

Well after ordering all my exhaust parts and having to wait a couple weeks to have them installed (Had to pay Uncle Sam first). I finally got everything in.
It's exactly what I wanted. No Drone with a little grunt. The only hint of a drone is when it's at about 17-18 hundred RPM and under just a slight acceleration.

It's a Magnaflow 5x8x24 SI/DO 3/2.5 with Corsa Dual Tips.

Also this is my first time creating a YouTube video.

Sorry for the crappy video, it's from my cheap a$$ little Aiptek camcorder and taken late today. Hope it gives an idea of the sound.

Here's the videos. If you go to YouTube you can see them in HD.

http://www.youtube.com/watch?v=j_khVW8u-gM

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

http://www.youtube.com/watch?v=XDVhqaBw2Y4

http://www.youtube.com/watch?v=t329M7dtJKE

 

Wow TheKR, that sounds very good for a 24" body. The 2008 & older can't make them sound that good with stock manifolds and cats. Very nice.

 

Thanks Darren. I know what you mean, my 05 didn't sound like this one with the stock setup. The stock muffler on this 09 even had a decent little tone.

Do you know what changed?

 

Sounds good man

 

Theres a couple changes, i'll start with the 2005 change.

In jan 2005 they switched to a two cat design vs the original 4 cat design. So if your trucks build was Dec 2004 & prior, it had 4 cats.

For 2009, they added less noise resonating converters, these cats are about as good as the GM catalytic converters now, there will be less demand for hi-flow cat swaps in 2009+ cause the stock cats are nearly hi-flow as is, your video is clear evidence, a 24" Maqgnaflow sounding that loud?

And the muffler in the 2009s is straight through with offset chamber walls to deaden drone, but does not flow like a chambered muffler, flows, and sounds, like a good straight through. S therefore, a good sounding stock system nearly.

 

I would not have believed you saying that is a 24" magnaflow!
I like it! Nice subtle and deep!