Well got the harman tl300 in and running. Everything seems to work good. It's already clear to me how much wood it's going to save. As far as the misterious after burnner I would describe it as the same noise that a furnace makes when it lights and runs. You can ocasionaly see the re-burn hapening at the back of the firebox. This thing does take some time to get the bed of coals that you need. Still learning but for now I'm nothing but happy. It does have a good light show but it's hard to get it on pic. Pat