355 OBD 1124 confusion?

For 348 models, 1124 is listed as purge valve, while for 360 models it is listed as long trim fuel trim additive air. Which would this be for 355 models?

In the picture below, #44 is listed as flush valve; thinking this could be the same as purge valve?

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Today I noticed that the cap of this valve was apart from the body, and the internal solenoid was disconnected from the its electrical plug.

Could this be my issue? Is it as simple as putting it back together?

Finally, I am not clear about gas cap, and gas tank pressure: Whenever I unscrew my gas cap, a good amount of pressure is released. Is this normal? Intuition is telling me this is all related to 1124?

 

Thanks.......for what I have read, I don't have any issue with my tank...just not what I am used to.