I'm looking for better fuel mileage and not necessarily more HP. What is the best chip or tuner out there for this?
What can I expect in fuel mileage increases or is it a waste of time?
The truck is a 2001 F150 with a 4.6 and 137,000 on the clock.

 

i would say a custom will get the most gas mileage but were only talking about 1 or 2 and even 3 miles on average and with the benefit of more power. A VMP tune (87 Gas mileage) will get you great results. you can even do a 93 octane gas tune and you might see a better higher average than the 87.