RE: Smoke test
I believe us short boxes actually have 26 gallon tanks.
You got big tires, 4.10 gears, and a brick of a truck as far as aerodynamics go. It'll take a bit before you start seeing MPG results from any tune-up/upgrade, usually.
I have 265/75R16s, 3.55 gears, K&N drop-in and NGK Iridium plugs, and I get about 10mpg right now (its also constantly below zero here right now). I am heavy footed as well.