I've never heard of a 5kCSTQ with an air-cooled turbo! I think all of them had a water-cooled k26. If some did have air cooled, I'd be very supprised and like to know more. I know the earlier Audi 5000 turbo cars, pre-1984 had oil cooled turbos which could be problematic, but never heard of any that were air cooled. Later, Dan