if the plugs are that sutted up it could be a lambda thats gone, cause it doesnt take much to fuck them up, i had a fairly new one on just before i fitted my cam and cause i had timings wrong and it was overfueling my plugs were completly black like they were just dipped in block power, and the car over a period of a week or 2 had run no more than 2 hours and when i finally got it running it missfired like a bitch it turned out that the lambda was fucked, and yet it was fine before i cammed it lol
but still best to check on the diagnostics to find out, could be 1 of many things that causes the prob
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