One more thing...
I'm about ready to start putting it all together and my obsessive nature is rearing its ugly head.
The gas pipe is near the duct and so I can see it. I'm sure they used pipe sealant when they put it together and I don't think there are any leaks, but would there be any benefit to adding more to the exposed threads just to be sure or would that be a bad idea?
I'm not talking about unscrewing the pipes and re-doing them. Just dabbing a little more pipe sealant around the exposed threads.