Seals, particularly the turbo seals. Most of the ads for the turbo cars I've seen say that the car smokes-- usually a valve guide or a turbo seal. You're also going to probably have leakage from the valve cover. Rot likes to pop up in the doors, especially if the window seals are bad (water goes in and never comes out). Unfortunately, with cars this age, a lot of things that wouldn't need to be replaced in the car's "normal" lifetime crop up (CV joint boots crack, shocks blow, fuel lines rot, brake lines rot, etc, etc). Older cars also love to develop electrical gremlins. That being said, if the body is reasonably sound, I would spring for it. With the exception of critical things like brakes, suspension and tires and fuel system integrity, the problems that crop up can be lived with or worked out in your own time. As you know, the little things that pile up often have a cheap and simple solution on these cars.