The black Plastic deal is the check valve.

I have seen two failure modes of this thing. One the plastic is just pressed onto the injector nozzle. If the plactic injector wobbles or turns easily...not the top threaded part but the entire body of the check valve it needs to be replaced. Next is the alumnum fuel line fitting in the check valve. I have seen these come out and the engine goes lean and backfires.

There is no way to fix either problem. Replace the check vlave, or just remove it and runa fuel line up there until you can get a replacement.

DO NOT try to remove it and then re-install it. The plastic material is made to go on one time and then it will crack when you take it off. So removing it means you need to throw it away never re-use this part.

The engine will run without it. Only after a long idle like in a spin will you notice any difference in the way it runs without the check valve on the injector.

Troy Newman
Team YS