I am goin to have to say that I love my set up, I have something very simular done as pictured above. I will post my pics soon. I have a 5.3 and I bought a X-Pipe, and then dumped the (2) Flowmaster Original 40 Series right where the stock muffler was, then put 2.5" turn downs on it. Sounds great, get compliments on it all the time, even from my FORD buddies. That is cause they are jealious!
About the Interior noise, well I will have to say there is a lil bit of a drone to it, but i like it loud. Whenever you pull out it drones a lil, and then while cruisin it is not bad at all, at WOT it is nice as hell and is doesn't drone much. On the higway it is not bad at all, the Xpipe is what hells out alot i think! There are my 2 Pennies for ya!

 

I had the 40 series single 3" in dual 2.5" out dumped like JDG, was cool (for about a week) cut the dumps took them out back. Forgot about the drone and cut 'em off again and 5 minutes later remembered why I got rid of the dumps. Dumped sounds great, but not for a daily driver IMHO.

 

now what are the advantages of true dual 2.5" compared to a 3" y pipe. Dont both flow similiar? Do most guys go for duals because of sound? Sorry for hijacking

 

I actually just had this done today. It's a flowmaster 40 series with dual 3" outlets. It really isn't too bad on the interior noise. There's a nice deep rumble to the truck now more than before. Like others have said, when you go WOT it just screams. I may end up getting tired of it in a few weeks, but it's no big deal cause the guy only charged me $34. The one complaint I have is that it's making the plastic under my window rattle really bad now. BTW, this is on a 4.8 and it sounds really agressive now as compared to before with the dual tailpipes exiting in the rear.

 

I have 2 40's dumped right after the muffler and JBA shorties.... my resonnance is less now than when I had tailpipes and 50's. I didn't beleive it at first but its true... dumps will lessen the resonance and give it a much deeper sound.

 

my experience with 40's dumped was horrible!!! they sure did sounded good, there is no doubt to it but with all the noise inside and the back window kind of rattling just wasnt good for a daily driver especially on long trips.... it fustrated the **** out of me!!! so i changed it, oh and I had one dumped and the other came out in front of the passenger tire with a camaro tip..... I did not have an x-pipe so I would not know how it would sound with one???

 

man i will never have flowmasters dumped. especially after having a flowmaster and then riding in trucks that have them. they have a drone noise on the freeway that will drive you nuts. i have dual with dynomax turbos and a custom x pipe. and at 70 to 90 i have only wind and tire noise.