burnt black tar-like substance on sparkplug?

[baja1]

just one plug,#2. junkyard engine I was told is a 2002 going in a '97. is there markings somewhere on an engine showing the year?
anyway what do make of this black substance burnt on one plug? the valve covers are off to do the gaskets, its really clean in there, no sludge at all. I guess i'll be swapping intake manifold and injectors
thanks!

 

[19963.4lsr5]

I don't see any pictures


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