PLEASE READ, # 1,3,8 pistons black

[fiveohpatrol]

i removed my heads tonight and saw that a few of the pistons were very gummy and black, what is this from? lately i've been having coolant problems and the plugs were getting a little wet, could is it just carbon buildup from the plugs getting ruined and not firing? this is really disturbing me and i wanna make sure it will be ok before i put it back together, thanks

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88 Notchback 5.0, 3.73's, Explorer intake, pulleys, Crane 1.7's, BBK headers, off-road H-pipe, flowmasters, subframe connectors, 65mm TB, shift kit, March ram air kit, motorsport wires, MSD coil, upper and lower control arms, 155lph fuel pump, cheap 2800 stall, Crane Adj.FPR, best time- 13.99@99.75, not yet tested times after rocker and intake install