This is a long shot, but figured I ask: Have an old Mac that is running Mountain Loin 10.8.5. The OS can't be upgraded for reasons that I wont get into in this post, also have an iPhone 6S Plus. iTunes 10.4.x was the last version of iTunes that would install on OS 10.8.5 but wont recognize a 6S (it will recognize a regular 6). I can't believe that there are any real major differences (sync wise) between the 6 and the 6S. Somewhere in the app bundle there must be a table of supported devices. I have searched for it but can't locate it. Does anyone know of a hack or modification I could make to iTunes 10.4 to get it to sync with the 6S?