The fuel injector has a "tip shield", kind of a cup with a small hole in it, down inside the injector hole. The manual says replace them when you replace the injectors. Problem is they seem to be pressed into place and hard to get out. After messing around with one for a very long time, trying to get it out without damaging it I gave up. If I had damaged it and couldn't get it out I was worried that I would have to pull the head to get them out. So, the originals are still in there with no apparent ill effects.