This is by FAR my MOST requested tune file I have. This is a CUSTOM tune file through and through. It is for a 03-05 DURABURB with an LBZ engine with dual tanks(can also be used in a truck looking to run dual tanks). This tune file allows the fuel gauge to show the total fuel for both tanks on your factory single gauge at the same time, and runs the transfer pump to transfer fuel from the rear tank to the front tank. It is currently scaled for a LBZ sender in the front tank, and a stock 03-05 BURB level unit in the rear tank. Changes are required to the BURBS wiring to properly power the transfer pump. It also is set up to turn the 4X4 indicator on in the cluster when in 4X4 if you hook up the wired inputs to the ECM. And it goes without saying it is for an ALLISON trans.