Fuel Tank pressure not equilizing......

The Metallic popping sound is most definitely due to a "pressure equilization" of the tank. Is there a way this tank does equilize the pressure either between the various levels in it, or to the atmosphere? I have googled and cannot find any info on it. I know the tank is plastic, maybe it is has something to do with the tank pressure on the straps. I am a car guy and have done various work on vehicles, but am not sure of the defaults in this tank / fuel system design and how it equilizes the tank pressure.

I am not sure, as now I have a P300 random misfire, repaced intake valve, checked compression, working on electrical, egr, etc.... But I think your issue should be purge valve needs replacing. a $40 part.