Until someone comes up with a better answer, I don't think there should be gas there at all! My understanding is that the screw simply adjusts the mechanical offset or ratio between position of the airflow meter plate and the plunger in the fuel distributor that apertures the metering slits. I.e., gas would only be present if there was already a leak past the plunger, and it dribbled down to the screw.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7