I recently bought an 04 lb7 CCSB that came with a bully dog triple dog GT tuner in it, has 305's on it and aftermarket exhaust. I have changed the air filter and just changed the fuel filter today. But I don't think that is the problem. Runs good. No diesel in the oil and doesn't smoke any that I can tell. The programmer is on the extreme setting but I don't get on it much. Could my injectors be starting to go bad and cause my fuel milage to be THAT bad? Filled up today and Was just under 13 mpg hand calculated. I have efi live to check the balance rates of the injectors but have to get my laptop fixed first.