I currently use a New Braufels as my primary smoker and actually run it opposite of the way the previous owner had recommended. I run it with the exhaust wide open as well as leave the firebox door wide open unless the outside air temp is below 40 degrees. The previous owner was more than likely adding too much fuel and therefore having to choke down on the airflow to lower the temps.
I run mine with mixed hardwood splits (oak, maple, hickory) about 2 inches in diameter and 7-9 inches in length, I typically have 2-3 splits burning at any given time to help maintain a solid bed of coals. If I find the temperature moving up I just move the fire further from the cook chamber opening. I would recommend using a water pan to both provide humidity and act as a deflector plate as the firebox/cook chamber opening is pretty high in the cook chamber. I have also elevated my grates around 4 inches above the stock grate position as I found too much heat was flowing over the top while barely any color/temp was hitting the bottom of the meat.
Hope you find this helpful, happy to provide more info/answer any questions you have.