first off congrats to the both of you on picking a fine truck, as for the 6 cyl. the only way to improve the mpg and performance is a gear swap, the stock 3.55 are not going to cut it, a nice set of 4.10 will get the truck to where you want it, all the engine upgrades wont do much but burn a hole in your pocket, back in 05, my gear swap was 1600.00 for everything, now that the truck has been out, should not be that bad, you will spend a good 1000.00 on engine upgrades, like intake, t.b. and computer