I would advise not doing anything with your firmware until someone with lots of experience flashing Pioneer drives answers that particular question. (Although after doing some research on the forum on that particular topic, I would say the answer is most likely that you *shouldn't* do anything with it.)
As far as I know, DVDFab, and most likely Passkey and therefore FindVUK as well, aren't UHD/4K compatible with Pioneer drives.Thought maybe the key is not yet in the database, so I fired up FindVUK 1.83 but it seems DVDfab can't read my disc.