i just bought a 2003 f150 super crew 4x4 with the 5.4. i hear bout people getting 13 to 15 mpg. my truck is all stock. when i bought i did a complete tune up on it. i bought autolite iridium plug, replaced all boots, springs, and coils with bwd brand. im only getting 11 on the highway and about 9-10 in town. i was told putting summit headers on it helps it breath which improves the mpg. i was looking around on the internet looking for a programmer. but i dont want to spend the money on one if it would help at all. i was wondering if anybody knows something i can do to improve my mpg?

 

First off you used the wrong plugs and COPs. That could be part of your problem.
But to answer your question a programmer is a hit and miss on increasing your gas mileage. You don't buy a programmer for the mileage you buy it for the power increase and the better shift points(the main flaw on the 10th gens).

Don't know where you live but by me right now there is winter blend fuel which ends up killing gas mileage in the winter.

Yes Long tube headers will help but once again can't guarantee a mileage increase. Look into Pacesetter header, OBX, Dynatech, or Stainlessworks headers.

How many miles on the truck? If a lot your cats might be fried and need to be changed.

If over 100k looking into changing your O2 sensors with either Bosch or the preferred Motorcraft O2 sensors. You have 4.