I just got a replacement D16Z6 for my 1993 del sol si. When I got it home and looked at it, there was what looks like a plug on the outside of the cylinder wall. It's about the size of a nickel and it has silicone upunder it. Can anyone tell me what this is and if I just got screwed? I would also like to know if this would make it worthless for me to put this motor in my car. Any input on this matter would be helpful.