What should I look for in a used Saab 9-3 sports?
To be sure a turbo engine at its best, you should always look for a full service history. Dealer stamps are best, but specialist marks are an acceptable second, especially on older cars. Beware of garages which don't know what they're doing - the turbo engines drink a particular type of oil, and only those who know what they're doing will have used it.
On a test drive, run the engine until it's hot and then rev the car when stationary. If you get blue or black smoke from the exhaust, then there's a good chance the turbo has failed. Walk away. And, do the same if there's any sludge on the inside of the oil filler cap. It's probably a sign of head gasket failure.
The hood mechanism is generally reliable, but there was a recall to stop the hydraulic pipes getting trapped, so make sure it's been done. And, as you would on any convertible, check the hood for wear and tear.