I have a early 99 F350 psd.38k miles std.cab duel wheel 4x4 auto. trans. with a 7.5'x9' omaha dropside stake dump body(GVWR 12.500k) Without any heavy duty use I`m getting about 10 mpg does this sound correct? This is my first power stroke, my 6.9 got 18 mpg. Also i don`t like the trans./torque-converter shift patterns. Much too quick. Fourth gear by 40 mph. Has anyone tried the trans. chips or computer reprogramers aftermarketers are selling? There supposed to be good for plowing and towing. Better preformance and mileage,so they say.