Nice mod! I'm experiencing a visual bug while the furnace is running, where the smoke generated by it rises very rapidly a long distance before slowing and blowing in the wind. Only this furnace is affected.

That's not a bug. The smoke is shot out by this boiler at a faster rate than the vanilla boiler.

I see. I thought that would make sense for a gas boiler, but it rises so high the magnitude of the difference didn't look intended. It is controlled by starting_vertical_speed in data.lua, right? Do you know the default boiler smoke speed is? I'm having trouble finding it in the base files.

I noticed while playing around with it that it doesn't seem to generate any noise either. Is that intended?

Yes, that sounds like the right data value.

The gas boiler does make some noise. The same noise the vanilla boiler makes. It's subtle. The steam engines usually are the more-prominent sound.