my Jimmy is running rough so I decided to pull the plugs today and see what they looked like, I went to pull the #2 plug and noticed it wasnt tight, so I pulled it out, its black colored, cleaned it and went to put it back in and it wouldnt tighten up, any suggestions on this? And then I pulled off the black round thing under the Vortec plastic to look for washing, and on the drivers side, if I shiined the light toward the grill and loked that way I could see a very shiny intake bolt- is this the washing from the nut kit?