Oil starvation causing issues with the turbochargers was an issue that mainly affected 991.2 version 911s, and subsequent revisions to the oil feed seems to have reduced the frequency of problems, if not eliminated them completely. Other issues to look out for are relatively minor in comparison, such as faulty door handles or failing active engine mounts. As you are buying from a main dealer an approved warranty should offer some reassurance, but it would be worth checking with the dealer to see if any mechanical updates from the manufacturer have been applied.