My brand new (at the time) 1990 D150 V6 5 speed got an honest 24mpg day in day out of commuting.
My 97 Dakota V6 auto 2x4 gets just over 18 in commuting.
Tuners are not magic, and if what the OP is saying is true, don't you think it would have become pretty much mainstream knowledge over the last 20 years?
