Pressure check and leakdown tests should give you some indicators, I had a turbo runner and had very few issues with it. I can only think of a couple problems with it but they were unrelated to it being a turbo, I did have the turbo rebuilt at around 230,000 miles and the #4 cyl. was going down when I sold it at 250,000. Overheating issues almost always lead to the head gasket if not attended to. Oh and a turbo runner will out-run a 3.0 any day of the week
