It is the Chevrolet fuel injector that supplies your combustion chamber with the correct amount of fuel as dictated by your onboard computer. The end of the fuel injector is actually in the combustion chamber and the reason is has to be periodically cleaned. Unlike other components on your Chevrolet, the fuel injector is not routinely pulled and cleaned. There is a special injector cleaner that can be added to the fuel which will help keep the end clean so it can dispense fuel into the combustion chamber. If this is not done on a regular basis, the end of the fuel injector will become gummed up which will hamper its ability to properly dispense the fuel into the chamber. In the new models there is a Chevrolet fuel injector for each cylinder of the engine. The old throttle body type of fuel injection only had one or two that dispensed fuel in the intake manifold for delivery to the cylinders similar to the way carburetors delivered fuel. To test the fuel injector on your Chevrolet, it can be pulled from the socket so that the fuel ejection can be viewed. If the fuel dribbles from the end, it is partially clogged and might have to be manually cleaned with solvent or replaced. If one appears to be like this it is a safe assumption that there are others in your system in the same condition and they should also be pulled and cleaned or replaced. An owner of a Chevrolet will also notice a rough running engine if the injectors are clogged along with a decrease in fuel mileage and very poor performance of the vehicle. Replacement is the fastest and assured way to rectify this situation. Some clogged injectors cannot be cleaned to work properly once they get too gummed up.