This morning loaded the intrepid pretty full with ash, cat engaged stove top 550 and pipe temp 18 in up pipe at 370. i usually hear a slight rumble from the cat area but this morning there was a very audible roar coming from that area...... i closed air almost all the way and it went away as stove cooled below 500. it kinda got me nervous but it did stop with air reduced. even with the roaring sound no temps were rapidly climbing. who knows, anybody else experience this. oh yea outside air temp is 14 deg f.