I just had this same issue on my 06. It turns out that it was the roll over valves (2 each on top of the gas tank) that was the porblem. I did have a cel. After the mechanic dropped my gas tank he found that both roll over valves had the stems broken/cracked and was seeping out gas fumes. evidently subaru has had a rash of these and parts are on backorder. I was lucky and mine only took about 2 weeks to come in and about 4 hrs of labor to fix.-john