we basically have the same truck, although you,ve got the bigger tires.I'd love to put bigger tires on mine(LT 245/75/R16) is what I've got now,but I can'just barely fit in parking garages now.I'm surprised at your gas milage I got 23 mpg on the highway on a trip to Foxwoods.Your tires probably have something to do with that,I've also got a chip and that helps a little.Its a great truck real workhorse drives a little stiffer than a regular F150 because of beefed up rear end for heavier towing and hauling.I paid $26000 off showroom floor added about $1200 in mods,I did trade in a 99 lightning for it, sticker on F250 was about $32000. so I got a good deal. The chip should be your next investmant you'll definately appreciate it especially since you've got the exhaust and air done already. Good Luck and keep me posted.
99 F250 XLT LD 4X4 S/C,5.4,3.73 Limited slip,Bright red clearcoat ,4whl abs,remote start w/keyless entry and alarm,chrome rims,tinted,westin nerf bars,factory tonneau,superchip,K&NGen II fipk,pioneer in dash cd,pioneer amp,infinity kappas all around,Lund front runner bug sheild.Gibson split rear,stull SS grilles.