I'm sure the MES gurus will be by eventually with better info but your problem typically arises from low air flow and/or thick smoke. You do not want billowy white smoke, you want TBS (Thin Blue Smoke). White smoke has more incomplete combustion products leading to bitterness and is usually caused by lack or air to your wood. You also want your top vent(s) open, don't let the smoke build up inside, keep it flowing, smoke buildup can lead to creosote formation - also nasty. Also, what are you using to generate the smoke - chips, pellets, dust, chunks?