986. Positive pressure when removing gas cap

[986Angel]

Hello Everyone

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am new to this communityTwo years back acquired my second Porsche, a 97 Boxster 986 in Guard's Red(first was a 2012 cayenne)

Recently, have been noticing a whining sound from the front right side of the vehicle after it's been driven for 30+

minutes on a warm dayabove 75F lets sayThen was able to pin point the issue to the gas tankWhen remove

the gas capget a positive pressuredon't have issues filling up at the gas stationsso am not suspecting the vent valve.

My purge valve works fine (tested with a diagnostic tool) am suspecting the gas cap but preventing hydrocarbon fumes from escaping is basically one of the gas cap functionso Idk if need to replace the gas cap.

The Charcoal canister and other hoses all look in good shape and functioning okay since the RMP does go up in about 5-7 mins which is when the purge valve opens up and lets the canister to empty out into the intake.

am stuck and need some help before take it into the shopam wondering if anyone have experienced similar issues and what was causing it

Thank you