Fuel mileage mods and alternative fuels

On my 02 Dakota 4.7 a tonneau cover was worth 2 mpg gain too like clhyer's was. Cold air kit did nothing but a slight power gain and alot of noise. Same with the Flowmaster cat back, no gain, just noise but it does sound good. Also tried a superchips tuner and it gained 1.5 mpg as long as I keep my foot out of it but unfortunately that's pretty hard to do with my lead foot and when you do get into it much it's worse on gas.