Earlier in the day, I had pulled the fuel rail off, the piece of plastic had broken off of the connector and fell down into the injector boss. I did not see it when I put the fuel rail back on, and when I pushed the injectors into place it just wedged itself in between the injector and the head. When I took the fuel rail off, the o-ring was tore, so I don't know how it wasn't spraying fuel all over. By the way, I put the fuel rail back on and the noise is still there.