A busa ridden nice and hard and twisted regularly to redline produces beautiful plugs, nice toasty brown.
Kevin you need to park your Busa indoors maybe? Someplace Dry anyway, and run that thing harder and hotter. My .02 anyway. If your plugs look like that, then you pistons are not far behind. You need to get some heat in there, burn the gunk out.
Remember, 87/89 octane and twist it like you mean it. If your not up to it I know Greg will do it for ya!