White exhaust smoke is usually not a good thing. Most times it's an indication of water or coolant which is not good unless it's just present when starting up. In that case it's just steam from condensed water in the exhaust system. Are you loosing any coolant? If so could be a cylinder head leakage problem. Bad news... Maybe try removing and cleaning the throttle body and flame trap. There's a small hose connection on the flame trap that gets plugged w/ hard carbon deposites and needs to be drilled out.