Q: When I unplugged the TPC it runs like a new truck

Hi there. If when you remove the TPS (throttle position sensor) and the engine runs better, then there could be an issue with the MAP (manifold absolute pressure) sensor. Check the MAP sensor and see if the harness is good and free of corrosion. If the MAP sensor is working correctly, then the TPS has lost signal to the input and needs replaced. As far as the engine back firing, that could be caused by a camshaft sensor failing or a burned valve. Check the camshaft sensor for if it is plugged in all the way and test the sensor with the engine off. Manually crank the engine over as you check the sensor to see if the sensor is reading a resistance. If the sensor is not reading a resistance or it has resistance on it all the time, then the camshaft sensor needs replaced. If the sensor is working correctly, then check compression on the engine to see if there is a burned valve. The compression should be 120 psi or higher on all GM engines. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from Your Mechanic, that can assist you with the engine running rough situation.