Now just to start this out I'm only looking for a couple of miles per gallon better so with that said...What sort of after market mods can a person do to get better mileage? I've got a 5.4 2001 Screw. Thanks in advance.

 

Save your mod money for gas. You'll be lucky to get 1mpg better after spending $1500 in mods. $1500 buys a lot of fuel.

 

On many of the mods web sights for let's say, air filter systems and exhausts, the companies say that in addition to getting more horsepower you also get better gas mileage. Is this misleading or stretching the truth?

 

Stretching the truth. Increasing the efficiency of an engine does generally improve fuel economy, but not by as much as the manufacturers claim. A vacuum gauge and a controlled right foot will get you more improvement than engine mods.

 

Fuel milage is all about keeping the throttle closed as much a possible consistant with getting to where you want to go.
This is how the 04/05 electronic throttle controls work.
Power is all about generating the most torque in the wider throttle openings.
Think about it: filters and exhaut don't do a thing, at low throttle openings, because the throttle body 'soley' controls how much air enters the engine at low power levels and the stock exhaust is more than adiquit at the same time.
For higher power levels, it's all about airflow. If there are any restriction in the flow paths then some xtra power can be obtained.
You cannot mix fuel milage with power in the same breath.
Rarely can you improve both without making internal changes such as raising compession ratio and optimizing how the computer controls the engine.
That said, it is not a simple bolt on low dollar deal to get any significent changes on these trucks.
My Screw weighs 5390 lbs with a 4.6 and I run 15 + mpg in winter weather and can go over 17 in the summer on an all stock un modified engine.
Also, look at it this way; at 15 mpg., a 10% increase is 1.5 mpg. Do you really think that spending nearly $800 in mods is cost effective and may not gain any fuel milage?
Your free to do what you want but take a good look at the situation before you spend.

 

I too was wondering how to improve my gas mileage because no matter how I drive my truck it gets 12 miles per gallon. Well, 11.8 if I drive it really hard and 12.1 if I drive it like a person that drive around town under the speed limit.

 

Proper maintenance and soft throttle can help. Synthetic fluids and reducing engine drag can help marginally, but are not cost effective (aka underdrive pulleys and e-fans). Basically, you drive a heavy, 4x4, supercab, aerodynamic brick with an inefficient engine.