2001 Cougar - Gas Smell

I have a 2001 V6 Cougar and since the cold weather started, I have been
parking in the garage, so I can't swear that this problem just started, but
I just noticed it.

I can smell gas fumes coming from the car and have located the source. The
fumes are coming from the grill just in front of the driver's side
windshield. I took it to the dealer and they noted that the fuel pump recall
had not been done on this vehicle. The fuel pump recall has been done now
and the fuel lines were also replaced at that time. There is no evidence of
a leak anywhere (no drips anywhere). However, the smell is still there. The
fumes seem to disipate after a few hours, and I have not noticed this when
parked outdoors, although it is likely just that it clears away faster in
the open air. I believe the car has the returnless fuel pump.

Does anyone have any ideas?

Thanks,
Greg

Update: the dealer has now checked the injectors and o-rings, and found no
problems there either. No warning lights have come on and there have not
been any codes.

when the car is first shut off, there are no fumes. About 10-15 minutes
later, the gas fumes begin. The dealer is at a loss as to next steps.

any input would be appreciated.

Thanks,
Greg