I must say this site provides a plethora of information. After owning a '03 and '05 Powerstroke, I just switched back to a F150. I came to this site trying to determine how to get the most out of my 5.4. I decided to go with the K&N fipk intake and a Flowmaster 50 series dual chamber muffler welded into the stock location. Prior to my mods I was getting 14.5 mpg city. After the mods I am getting 17 mpg. This is traveling the same route. I added a soft tonneau so I guess that could have help my mileage some. The system has performed flawlessly. There is no drone and I have noticed an increase in performance. Just thought I would provide my personal results.

 

If your looking for better mpgs, you can do electric fans, that should give you another 1-2 miles. Also, if you drive mostly city you can do some 4.10s, those will give you better miles in town, but you will lose 1-2 per gallon on the highway