Wrong heat range plug. You probably need to go up two steps. The base ring should not be carboned up unless it is pig rich. Try the hotter plug and then look at pulling some fuel out if it's still like that.

Remember, if you sit there and let it idle it's not going to reflect the cruise or power setting rich/lean.

You can always add an O2 sensor in to help you 'look into' the exhaust.
[addsig]