Just updating the post with a tune from the truck in case it might help.


I'll get pics posted shortly.

Tune: Turbo Sierra Tune

 

If your AFR stays at 14.7 while cruising like you say, then your tune shouldn't have any issues causing you to sacrifice mileage other than maybe spark timing, which I don't see any problems with in your tune. It's other things like tire size, gears, weight, etc that you would point the finger at then. You shouldn't even expect to see decent mileage at 1" of vacuum or in boost. While 10.2 is a bit rich, I wouldn't blame that for bad mileage. I'd blame it at your foot for making you go into boost in the first place.

 

"Lean is Mean!!" That's the quote, right?