This product has been our best seller for many years as it represents the most versatile power enhancement for 1998 ½ thru 2002 Dodge Diesel Trucks (automatically detects model year). It uses ALL the fuel available from the VP44 and makes an HONEST 100 horsepower at the rear wheels. Fuel delivery can be adjusted almost infinitely to make all users happy. It can diagnose almost all the fuel system problems from what can be displayed on the screen, and it even tells you when to replace your fuel filter or lift pump. It also can be set to cut back fuel enhancement automatically to prevent serious engine damage due to excessive exhaust temps. The FMS has more features than can be explained here.