Raw gas smell

I have a 2001 Subaru Outback with 142K miles. It is a great vehicle. One thing though, when it gets really cold, ie.: 0- 10 above, I smell raw gas. I had it checked last winter and no one found a leak. Well, it’s cold again, and I smell raw gas. It is so strong I open a window. Any idea what could be causing this??? Thanks.