First of all, I would like to tell you to be safe from the LPG gas flooding, As it can make hazardous Fire damage at home that can disturb everything at home. I remembered a few days ago the similar problem was going on at my neighbor's home, and thus suddenly the LPG catches fire which results into the blast at home. This made them calling to the insurance company for collecting the proofs and claiming the policy. But the insurance company was delaying the fact, so they took helpful hints from the public adjusters like public adjuster Los Angeles (www.alliancepublicadjusters.com/public-adjuster-los-angeles) for taking the process ahead.

Thanks.
It's throttle cable and air governor. I am curious about the diaphram vacuum on the back side of the mixer. 3 screws triangle shaped. No holes but curious to the purpose of it. Is it acting like a trim valve?

Most likely regulator issue. Especially if it's cable throttle with air governor.