Hello Put the manometer on the hose barb behind the fire box and got -0.27 wg after cleaning out the top of the upside down horseshoe ash chamber. So I cracked the cover to the exhaust plenum and to my dismay saw some very shinny creasote. It looks real sticky because it is real sticky! See pics. I removed the combustion blower and got out the Acetone and paper towels! Then some dry moly when clean! I do not see this very often. I know bad pellets can cause this. Could there be any other cause?