4.8 mpg killing me

05 14l Detroit pdi ecm stage 2 turbo getting 4.8 mpg. Replaced cac it was cracked in three places found cracked injector cup had new ones put in and bad injector replaced. Doing all that got me 4.8 its only money right? Feel better saying that if I was rich. Motor does not pull good when empty and is sluggish loaded but pulls better then when stock so what is wrong with it. P.s. new air , fuel filters , and overhead set and no codes don't want to throw anymore parts at it hoping one will fix the toilet. Like detroit wants to do.

 

Drive slow 61mph a lot and just because light turns green don't mean its a race. I have been thinking of that might be problem with sensors or ecm voltage just way truck was running at times. Would run one hill real good then next one would feel like you wouldn't make it have to drop four or more gears. No codes just hear motor sound different then be okay again. Like more knocking or rattling noise then normal. Just put new batts in 3 weeks ago. Going to check grounds and ecm wires. Thank you Mr. Haney for the advice. Noticed that the 14l don't get good mileage for some reason my cousin got same setup as this but 1 year newer and gets same mpg just can't pull a hill we haul 90 to 100 tho reg when in oilfields but haul light 80 or less when we go otr once in awhile. Was hoping for mid fives atleast.

 

When I replaced cac also put new bellows and clamps on. Nonwastegated turbo no vpod in trash can where it belongs along with everything else egr related. Ran cats for 23 years first Detroit learning there quirks yet. is it wires rubbing or just getting brittle from heat?