Bully Dog GT tuner off of a 2011 Chevrolet 2500 Duramax, I know it will work on trucks up to a 2014 model year, not sure about the 15’s. Used it on the truck to adjust speedometer for larger tires and the tow/haul option for a little more hp and improved shifting when towing the boat. Works great with a slight increase in fuel economy if you keep for foot out of it, which is hard to do.
$300
