imo it would gain you some yes. im going with a new exhaust from header back, i currently have tog headers , stock y pipe with stock cats and a dual in/out magnaflow 2.5 with x pipe, dual side exit before the rear tire. im going with longtube pacesetters ,magnaflow metallic cat 59559 x2 and a magnaflow 12599 3 in. dual in/out with x pipe. im also going to use a set of dougs headers cutouts and keep the same exit, shoul dbe in soon im not expecting a huge gain but some gain in top end!

 

i just switched from flow 40 for a magnaflow, and i am so glad i did, it is much more pleasant on the HWY and when you get on it, the sound is much better and i do feel a better SOTP

 

I do like the sound of the Flows on there. However, sound is not my primary concern. I want to squeeze the most amount of HP out of my truck as possible... if I am losing even 4-5 HP, that is worth having a not-so-cool sounding truck. Plus, I dont think the Magna could sound that much worse than the flows (I may even like it better )

Now the next question would be.... if the Magna muffler has an X-pipe built in.... would it even work that good if it was place at the end of the exhaust and dumped right after the muffler? (Turndowns about 6" from muffler exit). I ask this because I hear the X-pipe usually only works when its closer to the headers, because of exhaust velocity.

Also, I am looking to quiet down my exhaust in this process too. The 3" dual Flow-40's are WAYYY too loud for my taste. I would rather hear the blower whine than my exhaust now... its way too 'ratty' sounding since the Radix was installed. I want a quieter exhaust at WOT now.

 

Quieter at WOT??? I bought Magnaflows to have the stout tone at WOT, and quiet down at cruise speeds. I guess the Flowmasters are louder & more "ratty" @ WOT, huh? Now, I will say that I have a bit more drone than anyone would think (at least a bit more than I desire to have) because I had my exhaust dumped behind my dual mags before the rear axle. However, the trucks much more quiet than most I hear around town.

Give a listen (Old Vids):

Idle Tone <-- Basic tune... idled higher than desired (1000 RPM)
Driving Tone <-- Drove with window down in this clip

You can tell by that vid that I like goin WOT. I still wonder why my truck runs thru gas like a thirsty man runs thru water.

 

get spintech pro streets... AWESOME sounding/performing mufflers...

 

Well.. I want quieter at WOT than these Flowmaster 40's.. lol. There are wayyy too loud and raspy @ WOT.

As far as the Spintechs, I have heard a lot of good things about them.. and even looked at one before. BUT I noticed they are a chambered muffler... do they have any better flowing straight-thru mufflers?

 

not sure... check out their site I guess... even though they are chambered, they still flow pretty well.

 

I had true duals with "x" pipe and I ditched my flows cause one of them started to rattle. Went to 2 borlas and didn't like it (too much flow and no back pressure). Went to single 3" exhaust with one borla single in dual out and no tail pipes and love it. I guess that since I was running duals and the chambered flows, the backpressure was just right and now 3" and a better flowing muffler it amounts to about the same...

 

04evilSS i had true dual 2.5" flowmaster 40's and all I did was put a X-pipe right infront of them and took the rasp out. Might want to try that, its alot cheaper then dumpin a 150-200$ exahust system and puttin 200 $ more back up their for what little to no gains.

At the track if you empty your pockets and change storage you would probably net the same itmes as goin to the magnaflow from flowmaster.

 

on my 04 crew cab, 5.3 that I used to have I started out with a si/do magnaflow, liked the power, but wanted louder, so I switched to a flowmaster si/do. Loved the sound of the flow, but noticed an immediate loss in lowend power was no longer able to burn the tires from a dig. After that I went to a true dual setup with the magnaflow di/do with the x-pipe and it ran much better sotp, but it was too quiet for me, so I went to dual dynomax bullets and loved them, better power than the flows IMO. Just my 2cents cause I had always been a flowmaster fan, but would not run them again.