'04 Ram 2500 Cummins with 35" Nittos. Not being very tech savvy I chose to install Program #2 (towing) to compensate for the oversized tires and for more torque while towing our 23' toy hualer. Installation was easy, including recalibration of the speedometer. Better throttle response and more power were immediately obvious and my fuel economy increased by 1.5-2 mpg. The truck also tows our trailer with much less effort. I am very satisfied with the Smarty Jr.