Looking for mods that help on MPG.
Unfortunately your going to need to experiment as to what will give you
an increase in mpg. People can come on here and say this helped them out or that helped them out. There is no promise that any of that stuff will help you out because there are too many factors that come together for mileage efficiency some you can control others you cannot.
More often then not people that say "this or that boosted my mpg" can't really say definitively that one mod truly did it boost it. Most people's best level of evidence(by most I mean atleast 51% as that would be technically most) is that "I did this mod or I started using this and then I noticed an improvement", while that mod may have contributed to that improvement, there might have been something else that did as well in conjunction with that mod. Might have did an oil change or even switched to synthetic oil(I have calculated better mpg readings when I have fresher oil in there). Wind may not have been bad or maybe driven in terrain that wasn't as harsh on efficiency(not as hilly etc).
Most people don't take into account the other variables when they do their calculations, it's usually miles driven compared to gallons consumed, that really doesn't give you percentages of what went there. If you knew an exhaust system contributed say 7% towards efficiency, it would take awhile to pay for that exhaust, same with the tuner.
I'm not saying the things listed above didn't help mpg, they very well might have, but how much did they help? That will help in determining if it will pay for itself for your use during the time that you will have your truck. Only way you'll know rough precentages on what contributes how much to mpg is if you do a whole host of other calculations considering other facts that I know I wouldn't do and I'm willing to bet damn near everyone else doesn't do them either.
The moral of this long winded post is in doing mods you might want to put focus on something other then mpg efficiency as your primary focus, while you might see an improvement, how much really goes to that mod you did isn't easy to determine definitively.