Chevy Chevrolet Duramax Fuel Injector Control Module.
The FICM tells the injectors when and how much fuel to deliver to the engine cylinder. A symptom of a failing FICM is 1. loss of power 2. poor fuel economy or 3. cylinder misfires.
However, an overlapping issue (3) that could cause cylinder misfire is faulty coil packs and spark plugs which is why we recommend checking those as well.
The other symptoms (1, 2) mentioned could also be caused by a faulty fuel injector, clogged fuel filter or bad fuel pump.