Plumbing – Measuring Incoming Gas Pressure to Stove

If the pressure you're measuring is the static pressure, that is the pressure in the line with no gas flowing, that pressure is the same everywhere in the line. You cannot increase that pressure by removing unneeded gas pipe. Instead, you can try having the gas company adjust or replace your regulator.

If you're measuring the pressure while gas is flowing, you might have lines that are too small, long or bendy. You might also have a gas meter that's undersized or defective. I again suggest calling the gas company to see if the meter needs to be replaced.

It's really in everybody's best interest to just call a pro. But the gas company should be happy to at least answer your questions, since you're trying to use more gas. If the meter or regulator needs service or replacement, they should do that for free.

It is (very) surprising that the gas company (Xcel) says "everything's fine." This document from a different gas company certainly calls out non-blue flames as an issue that needs to be resolved. As does this site. And Xcel themselves.

Happening on all appliances does seem a bit less likely to be "and suddenly the air adjustments on all three went whacky" than a contamination issue - possibly water in the gas line?

I wonder how your furnace tech visit went, and what your neighbor's flames look like.

Editing post-comments: Ultrasonic humidifiers make small water droplets (without evaporating the water first) and then those small droplets evaporate while floating around - if the water contains salts or minerals, any salts or minerals in the water will end up floating around the house as tiny specks when the water evaporates from the tiny droplets. Those, evidently, are what is contaminating your gas flames as they are sucked in along with the air required to burn the gas. Old-style "sponge" dehumdifiers (should) only result in water vapor in the air, as they actually evaporate the water (and this eventually leads to a build-up of scale and salts in the humidifier and its sponge element, as those do not evaporate.)