I've got the 4.6l. Im not concerned about more power or better fuel mileage......I am but, I'll be honest and immature......Im more interested in a nice low growl.

Would just replacing the muffler be beneficial or is it necessary for a full cat back system? Which mufflers have a good sound & as far as Flowmasters go.....whats the difference in series?

 

i think flowmaster has 2 and 3 chamber mufflers. 2 chamber being lowder.

They also licensed their design and there are some knockoffs now. i heard an older chevy with a 502 that had these and recognized the flowmaster sound and he told me about these.
don't remember the company name but they were less money than flowmasters and sounded the same.

they do , by far, have the best sound

keep us posted.

my immature side also wants the buddies/ passerby's to KNOW i have aftermarket exhaust hence i would want the duals out the back.

but, still paying for the 33" BFG's right now..... maybe santa will be kind

 

I have an '04 F-150 Lariat Screw with the 5.4 Triton V8, which had a subdued, but nice exhaust sound with the stock factory muffler and 2.75" diameter, single exhaust out the right rear side of the truck. And on my first two tanks of gas, I averaged 16.4 MPG, with about 30% of my driving being around town and 70% being on the open road at 60 - 70 MPH.

Before I ordered my truck in early October.....I decided that I wanted to put some type of aftermarket "PERFORMANCE" exhaust system on my truck after it had about 1000 mlies on it. My BIGGEST reason for wanting to do that was to get better overall vehicle performance, ie: increased horsepower, increased torque, better acceleration, better pulling power, increased gas mileage, and lower underhood operating temperatures.....WITHOUT a substantial increase in exhaust loudness.

So while my truck was being built, I spent a lot of time talking with design engineers and technical "experts" at Gibson, Borla, Flowmaster, and several friends that work for NASCAR racing teams here in the Charlotte, NC area. After taking EVERYTHING they told me, and all other factors into consideration, I designed the following exhaust system for my truck:
(1) 2.5" to 3.0" x 6" long expansion pipe to connnect the following muffler to the 2.5" mid pipe coming off the stock catalytic oxidizer
(1) Flowmaster 70 Series, Big Block II Muffler, # 530702, with a centered, 3" diameter single inlet, and dual 2.5" diameter outlets
(2) 2.5" diameter aluminized steel, tailpipes formed/bent at a 65° angle just after they exit the muffler outlet tailpipe connections.....so they will exit out the right side of the truck, centered between the rear passenger door and the wheel well opening.....just like the SVT Lightning and/or the Harley Davidson F-150's
(2) 3.0" diameter x 18" long, polished 304 stainless steel exhaust tailpipes with slant cut tips
ALL connections are continuously welded, NOT clamped!!

I had a friend of mine (who is the manager of a local MIDAS shop), do all the cutting, bending, fitting, and welding on my system; it REALLY looks "factory" installed.....looks great and sounds great.

But BEST OF ALL, it performs substantially better than the original factory muffler (which by the way is huge and very heavy). I got 18.7 MPG (a 2.3 MPG INCREASE) on the first tank of gas I ran AFTER installing this new system, with pretty much the same driving pattern as listed earlier. WOW

I am sold on the system I designed and installed on my truck. From my own experience, I can tell you that it really does help to talk with "people in the know" before undertaking this type of project!!

 

fanman. did anyone discuss lean condition or anything regarding that. maybe the NASCAR guys. I understand for example from someone i talked to at SEMA that a prototype K&N aircleaner improved performance but may cause a lean condition on the 5.4 3Valve. By the laws of physics energy is conserved, so the increase in mileage has to be the result of less fuel burn per stroke or simply less work going into pushing the exhaust out, hopefully this is simply the latter.

I just know when you "Pipe" a two stroke engine and do nothing else. you will melt down........... recognizing that 2 strokes are much different than 4 stroke motors... just a question, because i am interested in this.