I'm running an older Whitfield Pellet stove, upon starting the stove i've noticed the flame becoming lazy and the door glass darking. After research I completed all the usual suspects door rope gasket, cleaned exhaust piping, ect. with no success. Upon lighting the stove i've also noticed the damper has no effect on the flame? Also i'm getting little or no exhaust air outside the home? Could there be a plug between the combustion fan and the fire grate? Also, the low limit switch seems to wants to trip because very little hot air is reaching the fan/exhaust area of the stove. Can anyone tell me on the WP4 stove door were specifically the airwash holes are at? Thank You. Suggestions???