The 21000 Performance Module. its 6.6L GM Duramax trucks (LB7 engines) from 2001 thru 2004. This diesel performance module is designed for fuel economy improvement of up to 20% and up to 30% increase in hp. Adjustable with a four position switch you can adjust the power on the fly, Stock, +30 HP 60 HP, & +90 HP. The module doesn’t flash the ECM, instead it receives the data from the ECM, optimizes the signal to the engine improving the fuel efficiency and power. Plug-and-play connectivity means there’s no need to cut, splice or modify engine wiring.