If an injector is faulty on a vehicle with high mileage chances are the remaining injectors are in a similar condition, or will be in the near future. Replacing your injectors as a set ensures each cylinder is receiving the same amount of fuel leading to better performance and improved fuel economy. Since the time required to replace a single injector is about the same as replacing all the injectors it is recommended to replace them as a set. Вот Что написано на GM . смысл в том что лучше менять все сразу ( Я понимаю что хозяин барин )