I get the tickets too, Many times I'm in the shop and I"ll go out and bullshit with the delivery guy. Don't think there is anything hinky going on there.
I don't think there is any soot as it's just out the side of the shop with a pair of 90's like a periscope. I would think I would see something on the building. Should the exhaust be thick white? If it was a diesel, I'd say it has a couple bad injectors
(or bad rings) Seriously I get a ton of white vapor out the exhaust, I always thought that is just water vapor. I know there is a seperate condensate line.
As far as the boiler goes, I don't know what I don't know. I put a call into the company that installed it, haven't heard back yet.
Do you think i'm barking up the wrong tree or could there be an issue with the boiler I'm not thinking of? I know there is no way I'm getting 900 CFM of air moving thru the shop as your calcs say.