Sorry to beat the horse but here is my situation. 2008 5.4 screw. I drive 40 miles to work every day all interstate and I am more interested in a tuner for fuel economy. here are the 2 im looking at..

Gryphon

or

Bully Dog platinum gt gas

 

No tuner will help with gas mileage. I don't care what their claims are. I drive 44 miles a day and use a Gryphon on mine. I am usually at 16.5 hand calculated.

 

There are many other reasons to have a tuner:
More gauges that are not on your dash
Speedometer correction
More power
Better throttle response
Better shift points
Code reading and storage

Just to name a few.