The one thing that I have noticed in reading all the various post on V10 mileage is the difference between older units and newer units. I think if you do the research you will find the newer coaches are bigger and heaver than even 10 years ago. Every one wants more and more slides and amenities. If I had the time and interest to do the research just how much heavier the average 2014 coach is over an average one from 2000.
The one mod to this setup that seams to help mileage is the transmission controller that reduces the early down shift by the transmission.
Bill