My 1970 911 T keeps having plug issues on cylinder 4, the plug soots up and affects the running of the engine(low on power) the car has new PMOs and has been on a rolling road 3 times but after a couple of hundred miles the same thing happens, I’ve tried hotter plugs but again the same cylinder and the plug soots up
The plug in the pic has less than 300 miles, all the other plugs are clean, what could be causing this and what could be done to remedy it
