Had a good boil last night. 250 gal in 5 hours from match strike to shut down. When rolling good stack temp stayed in the 970 to 1070 range. Smoke is starting to clear was still black at firing but changed to whitish when rolling good. Set up was squirrel cage blowing in ash door from a 6" piece of duct, ash door completely removed. Blocked area of grate inside door with a row of fire brick and also area at back of grate as well. Good even boil. Consistent draws. Once going good was firing based on stack temp. Average from start-up around 50 gal per hour, was above that at peak boil. Boiling 3.2% sap.

Thanks for all suggestions. Might try a bit stronger fan in the future as I still feel we are lacking a bit of air.