Injector Sleeves
WARNING: This page is about a different car, the 2004 Ford Pickup Heritage. However, it is still accessible from the selected car via links, so may be relevant.
The injector sleeves are placed in the injector seats. The gasoline fuel injectors are placed in the injector sleeve seats. When the gasoline fuel injectors are de-energized and the CNG injectors are energized, the sleeves bypass the gasoline fuel injectors, delivering alternative fuel into the intake system and providing a path of fuel flow from the gasoline injectors.