2005 Chevrolet Truck power reduction

There is going to be a diagnostic fault code stored in the Engine Computer. Many auto parts stores will read the codes for you for free. It's important to understand those codes will never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part is referenced in a fault code, that part is actually only the cause of the code about half of the time. Wiring problems have to be eliminated first.