White smoke's a sign of unburnt fuel/oil, the racket you heard was the excess fue/oill in the cylinder. Any chance you could have been at such an angle that you started sucking in engine oil into the intake somehow?. It's scary because that's a good possabality of a runaway (def. http://tinyurl.com/7z5yzob ), if so, you're lucky it choked rather that accelerating....Mike