I get 9/11 city/hwy with my relatively stock 03 supercab, 315's on stock wheels, 4.30s (stock)... I do 75mph @ 2200rpm (corrected via gps) with this combo and get a little over 11mpg on the higway... have a magnaflow muffler with stock tubing... did not do anything other make the truck sound nicer and MAYBE a couple of ponies more (able to keep the truck in overdrive longer on steep grades)... the next mod I do will be the SPD y-pipe, then a drop-in air filter from AEM, and definitely a tuner from 5-star at the end... I hate downshifting the truck, as that is what kills mpg (75mph @ 3300rpm in 3rd gear)...

Joey