took our first big trip with the rig down to Harlan, KY and WOW, all I can say is absolutely f'n awesome!!!!!!!! It couldn't have towed any better, it handled so well I was amazed.
Put in a prodigy P2 brake controller, added the DP-Tuner decel tune and had them change the shift PWM. I got between 7.6-8.5mpg, didn't matter if I went 65 or 75, the truck had the best powerband at 2200-2500rpm, so I set the cruise at 70mph (2200rpm), had absolutely no issue in any of the Kentucky mountains. EGT's running the DP-Tuner 20hp tow tune never saw above 1250deg holding it to the wood at times too. I also upgraded to a 6.0L transmission cooler and the trans stayed at 165deg in 95deg heat hauling through the mountains.
I literally couldn't have been any happier with how well it all performed.