Here's a close up shot that shows that I think it IS pitted. So likely this is not in good condition then?

So where does the "extra" fuel come from. Are you saying that's a bad thing to have extra fuel in there or that is just a matter of how these engines work. That there is extra fuel in there to aid compression, but with an extra hot plug more of it combusts, or detonates causing damage?

lastly - how does the shim help? By putting more space in and releasing some compression?

sorry for my questions I just like to understand thouroughly when I am informed of something new

Thanks