Yes and no. For the most part, improving fuel mileage on these trucks is a moot point. You can do all you can to optimize it, but seeing any kind of substantial gain is equivalent to chasing a unicorn. It has more to do with your driving habits than any other single factor. If I put my foot in it all the time, I can almost watch the gas gauge needle fall. If I chill out, not so much. It's all relative.
Tuned w/ 285s and an airaid jr, I'm averaging 14-15 city. If I set the cruise control on the highway, I can eek 17-18 out of it, 19+ if we're going downhill with a stout tailwind lol. It wasn't much (if any) worse before the mods, but it's a hell of a lot more responsive and fun to drive now. That's really what it's all about.