MDN

I have a 2000 Outback wagon. When the outside air temp is below freezing, I get a fuel odor inside the cabin when the car is at idle. The colder it is outside, the worse the odor gets. My mechanic and the dealer mechanic have both tightened all the clamps on the fuel lines. Things have improved, but the problem is not solved. Has anyone experienced and sucessfully solved this problem? Thanks