One thing to do is check the turbocharger. Climb to altitude (up
around 18K or so) and pull the RPM back. See how much MP you can get.
[Merlyn used to have a nice chart - might be on their web site.] A
worn turbocharger won't give rated boost up in the thin air (but almost
any piece of scrap metal will give lots of boost down low).

Check the turbocharger housing very carefully for cracks. Case cracks
are not uncommon. Induction leaks are also a pain (usually trivial to
fix, but can be hard (timeconsuming) to find).

OTOH, there is no reason why a well maintained system shouldn't make it
to TBO or close to it (new TCM cylinders being the exception - they
tend to last 400-700 hours, period!). I fly a turbo Arrow and really
enjoy the "high flight." I won't say I wouldn't buy a non-turbo
aircraft, but it would be hard to give up the turbo after having one.