Wow what a wild ride!
Intermittent issues are the worst.
Similar issue and "fixes" reported since 2012: See?
See also 15 June 2022 VW Technical Service Bulletin (TSB) re winter/summer gas quality issues:
Vehicle manufacturers already account for the Reid vapor pressure (RVP for volatility of the fuel at a set temp whether summer/winter gas) using O2 and MAF sensors. California gas has higher Ethanol content which affects RVP.
Fuel initial boiling point is 95 °F (35 °C) at sea-level.
Fuel boiling point inversely proportional to elevation.
Winter blends have lower boiling points than summer blends.
Vapor created at boiling point.
Lean fuel trim means more air entering intake than ECM expects (ECM adds fuel by pulsing injector/spark more).
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Rich fuel trim means less air entering intake than ECM expects?(ECM subtracts fuel by pulsing injector/spark less).
Purge valve is solenoid which is either open/closed. Anything in-between is a failing condition. A scope would be necessary to catch this behavior.
This issue could benefit from a dvom, scope and a good diagnostic tech. :-)
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