I installed a AG/ Diesel Solutions tuner on my 5 th gen ,before installing it i was getting great fuel mileage,then took to dealer for a service (was still under warranty for service) my only reason, they said they had to program a emissions program which i told them not to do!,but they claimed it was LAW,(********),MY FUEL MILEAGE dropped considerably, so i installed this plug an play tuner got mileage back an power back cauae it brought the fuel rail pressure back to where it was before the program that was installed to take it away,if your driving between the 1500-1900 rpm im getting around 19 mpg before tune was 12-14,