The plug in my #5 cylinder fouls up after about 250 miles or so. At that time the engine starts missing slightly and I clean it off and it runs great for another 250 or so miles. Its an oily deposit. Would installing a hotter burning plug in the one cylinder help this out? Can I just place a hotter burning plug in one cylinder and keep regular plugs in the other 5 cylinders? The engine/valves have never been rebuilt and other than this issue the car still runs fantastic. And yes it does blow some blue smoke more so till it warms up. Chris - 69TR6