The GT Diesel tuner unlocks more horsepower and torque to meet the unique demands you put on your vehicle. With shift-on-the-fly tuning*, customizable gauges to track performance, and better control of defueling and regeneration, you’ll be able to summon the low-end power to take on tough jobs or improve fuel economy for long highway hauls. Space for up to 10 custom tunes helps you adjust for the many ways you put your diesel to the test.