Is your fuel stored indoors, or outdoors where it is cold? Cold fuel is harder to ignite.
You can reduce the firing rate but you need to be sure you get enough heat there in MN. You would need to adjust the air to maintain efficiency.
You might need to do something about the ignition transformer. I have not had a problem with mine since the burner was replaced and I got a higher voltage transformer with it.
Increasing combustion air too much reduces efficiency. It should be adjusted by someone with the instruments necessary to measure compustion efficiency.