Well I'd NEVER would have a diesel pusher. Too expensive, high repair bills, complexity, weight, and 45 other reasons. 2 1/2 weeks ago bought a Fleetwood Discovery on a Freightliner Cummings chassis...
Fiesta....Congratulations.....Wait until the engine breaks in a little....somewhere around 11K-13K. It will pull a little harder and get even better mileage. Let the Allison do most of the thinking. When you approach steep grades, leave the cruise on and manually drop to 5th about 200 yards before you start to climb. You'll be amazed at how well it will work.
Lastly.....diesels don't accelerate, they gain momentum!