Alright guys, the part your talking about is called an injector pintle cap. The problem is that these things are next to imposible to find(trust me I tried). If its just cracked and is fine other than the crack i would say don't worry about it. If the cap is cracked to the point that it won't stay on the injector then your in the same boat I was in not too long ago. I had to have the injectors rebuilt to have this cap replaced. i recomend rebuilding them any way because it is inexpensive(10-15 per injector) and ensures you that your injectors are in prime condition.
