Wow, I didn’t know woodgas eats zinc. A lot of parts under the hood are made of Zamac, ZA 30. Most carburators and throttle boddies are made out of it. The intake manifold on my Ranger is made out of it.
In the oil and gas industry ‘sour gas’ is usually dihydrogen sulfide (H2S) which combines with condensate water to form sulfuric acid (H2SO4). Is that what’s going on here?