Fuel venting

[GAHorn]

You say you have "new" fuel caps. Are you certain they are correct for the aircraft, and are vented?
The "goose" neck vent does not allow fuel to be sucked out due to any relationship to any "low pressure" area, I don't believe. But it's been well documented that the vent will discharge fuel in a rapid deceleration if the tanks are near full. This was discussed in WD Thompson's book, and was initially noticed during heavy braking during wheel landings. It is a contributing reason the vents were later relocated on subsequent models. Fuel vented onto the cabin roof may also create the smell of fumes inside the cabin.