What kind of gas are you buying? I had the same problem with my brand new truck. Took it to the dealer and got asked that question. I said "down on the corner". Leanne said "don't buy cheap gas" and then turned away. I fill up with Chevron exclusively and it runs smooth, warms up faster, is more powerful, responsive and gets better mileage!
2006 4.0 5 spd auto 4x4 Super Cab
BF Goodrich Commercial Traction T/A's
Royal Purple Throughout
Alpine Head Unit with some Infinity Noisy Stuff