The definition of a rule is  an official regulation, code of regulations or set practice. An example of a rule is that a red light means stop. An example of a rule is an employer demanding their employees arrive at 8am.
New injectors cost anywhere from $80-$120 apiece, making their replacement a somewhat pricey endeavor. There are three types of injector leaks-it can leak fuel into the manifold from the nozzle, it can leak fuel into the engine compartment from the fuel rail, and it can leak air (vacuum leak) from the manifold.
Fuel Injector cleaning is no longer recommended by many vehicle manufacturers since the switch in design to cope with alcohol fuels. The new style Fuel Injector for alcohol blended fuels is made of plastic and is about Â½ inch in diameter. The new style Fuel Injectors typically fail from overheating but rarely clog up.