As promised in another thread here are the pics of my primary air adjustment screw, I'm sorry the photo is a little fuzzy. The two round discs are the factory installed secondary air flow adjustors. the issue I and some others have had is very high flue temps and short burn times. After a lot of playing around I did a couple quick experiments with tape blocking off part of the rectangular holes ( the primary air tubes leading into the upper chamber). The results of the quick tests proved favorable and prompted me to make a real adjustor. I actually looked very hard at how the EKO boilers are setup and how guys were modding their adjustors, I decided on the screw type coming out through the front do to the confines of my install. I simply drilled two holes in the cover over the center of the tubes and welded nuts to the back side, a piece of 1/4 all thread for each, and piece of 10ga mild with a hole through it in the center, a nut on side facing the tube with a tack. I am still tuning but have found that if run between 3 and 5 turns out from closed on the new adjustors and 3 turns out on the secondary screws, my burn time jumps from 1-1.5 up to 2.5-3 hours, I see no loss in heat output from the original design. My flue temps dropped down from mid to high 500's into mid 400's. Like I said I am still tuning a bit, trying different combinations of air to settings and seeing what each does. Bear in mind mine is the smallest econoburn, it is a 100, there is another member on here with an identical boiler that did not have the high flue temp issues so clearly there is some variable that we can't physically see. The top pic is the back side of the fan mounting plate with all four adjustors installed, the bottom pic is what the air channels look like behind that plate.