Gas fumes in cabin area via ventilation system

I have a 2001 Subaru Outback Wagon 2.5 with a 4 cyl. For 2 years now I’ve had the issue of gas fumes coming into the cabin area through the ventilation system. This usually occurs in the fall and winter when I start the car with a cold engine. Now it’s happening during the warmer months when I start the car after it’s been sitting for a while. For the past 2 years I’ve taken the car to the dealership and to a ma & pa shop… all they do is check for leaks, tighten the clamps on the hoses and send me on my way. Once the dealership actually changed a hose or two. This is still happening. Does anyone have suggestions on what to do next? I don’t want to be driving down the road and the car catches on fire.

Have someone check if any of the fuel injector O-rings are leaking. Leaking O-rings will sometimes leave witness stains on the manifold where the injectors mount. It takes very little gas to create that smell.