Subaru gas smell in cold, high altitude

My 2001 Outback has a strong smell of gas at high altitude in cold weather. It is intermittent, but overpowering. The dealer (at sea level) checked it out and found nothing. Any ideas?

There is a known issue with some Subaru models of that era involving gas line clamps that loosen in very low temperatures. The dealer should be aware of this.
I suggest that you try another dealership.