I have a 99 F150 SC 4x4 w/ the 5.4L. I have ordered the superchip flip chip, along with a K&N Generation II Fuel Injection kit. I have thought about adding dual exhaust to help compliment my new accessories, but have never been sold on them. I don't want anything too loud, something that is on the quiet side, yet provides the needed air flow I am pursuing. Any and all opinions are welcome, whether loud or not! What do you think?

 

Banks is now offering a "Powerpack" that includes headers, induction (K&N FIPK) and cat-back system for the 5.4L F150 & Expedition.

 

I have a 2000 SC 4X4 5.4.
I installed a Gibson single 3" in dual 2.5" out (behind the rear tires) on mine, and I LOVE it. It has a great sound, but there is no hum in the cab like the stock muffler had. When I pull a trailer or get on it, the sound is GREAT.
I bought the muffler from Carparts.com using one of their online coupons (that I found on this website) which helped me keep the cost down.

I hope this helps.

 

http://www.cgsmotorsports.com

Not loud like a Flow, but nice mellow sound.
I ordered a SI/DO muffler from them and had a local shop install. Noise in cab is not much louder than stock.

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93 F-150
CGS Motorsports SI/DO

92 Ranger
254,000 mile daily driver