My 7.3 went from 18 mpg to 20 mpg on the open highway with a 80 hp econo mode.
My automatic transmission program is by California's tranny guru, John Woods. It goes first gear, second gear, third gear, torque converter lockup and then fourth gear @ 47 mph. Feels just like a 5 speed auto.
Most of the tuners work better on the older trucks. The DEF diesels already have so much horsepower that more power's not really needed. I do believe that a good tuner could write a program that gives the new high hp models better driveability and general feel. But it's not worth losing warranty over.