When I'm tweaking my secondary air adjustment, there doesn't seem to be an appreciable difference in the "look" of the flame in the refractory tunnel from one end of the adjustment scale to the other. At least not what I would expect to see compared to the manual. Is this what you guys are seeing in yours? Also, can someone shed some light on the internal workings of this mechanism? Is it possible for this to become "dis-engaged", etc? It seems as though it's loose, or poorly attached...??? I've found that if I pull the lever down, and slide to adjust, I have to bring the lever gently up to the set position; if I just release it at that point, the airflow will be significantly less than when feather it into position. I found this out by experimenting with the boiler cooled down and monitorng the airflow in the refrac. slot by feel. This is starting to drive me cuckoo because I think this adjustment should be pretty straight-forward. Any observations are welcome. Thanks.