not the expert, but if I ran across that I'd suspect a po had put a hotter plug in one cyl to take care of some problem like oil fouling - the socket not fitting just means it's a different size - there's a variety of socket sizes for various plug types/manufacturers - the lack of elbow on the wire just means that one wire was replaced seperate from the set, or maybe it just fits the space easier that way - if plug wires don't come off right away, try twisting first to break it loose, then pull
Bill
