I too have oil burning smell when I stop which is a cause of my valve covers leaking some oil and burning when I drive. It's on the list to have serviced in the near future. I'd recommend taking it to a shop and having them put it on a lift so they can look underneath for what the issue is. It could be the valve covers or a number of other easier to replace leaky hoses caused from the age and miles on the car. I wouldn't jump to the turbo being the cause of the issue.

Subaru head gasket issues were worst on the NA 2.5l engines (like ej251), much less of a problem with the turbo cars. Should not be an issue at 120k. As mentioned above valve cover gaskets leak, passenger side is right above the up pipe and EM, so smelly mess. Fixable, but a bit of a pain due to the lack of space.

Timing belt been replaced? Steering rack leaking? Plastic radiator still? Biggest issue is rot on the rear strut towers, not easy to spot unless you pull the rear seat and rear trim, though you will see signs of really bad cases in the wheel wells if you pull a wheel and use a strong flashlight. All GD wagons have this flaw, the question is how far gone is the chassis.

^ That's the stuff. How this problem is still mostly a secret is beyond me. There must be tons of Impreza wagons/9-2xs driving around just about ready to push the strut into the cabin and go low rider.