che4ck your fuel pump, the stupid nylon fitting at the top is a known source of leaks, this is what was happening to mine after i got it. mileage started to get worse and then finally terrible and i could start smelling gas everytime i got out of the truck.

this is a recall issue in canada.

i am seeing around 300km's every tank now with the 31's so i am guessing that should actually be approx 350 to a tank. and i was getting about 400kms to a tank with the stock tires and the leak.

2000 SPORTY, DEF BOY customs, mmm....lockers, mmm... gears, mmm... double transfer case, mmm... stroker
http://www.cardomain.com/ride/2377991