[Discseven]

Paul... older 911s will eventually have hose and gasket issues. A '15 seems too new for that but who knows. Rather than something rotten I would suspect something "loose." Provided newer 911 fuel runs are like the old, there's the fill, vent, pump, return, and a hole in the tank for the fuel level sender. I had a worn level sender gasket so when the tank was near full, the cabin smelled of fuel due to that gasket leaking. Low fuel in tank... no smell. That leak was not severe enough so fuel could be seen below the car when it was parked. It could easily be spotted by looking around the sender. Am not saying it's the sender gasket but rather that being the simplest thing to check. Next I'd suggest looking at the filler and vent hoses. To check below the tank, I imagine there's a panel or more to remove.