How did you go with the pinging noise, my brother just got a new MY15 SSV ute with auto & it has the same noise you are explaining, I haven't listened to your video's but I don't have to, I was thinking either pinging or maybe exhaust leak somewhere but I don't know much about them so don't really know.
The first tank was a freeby from Holden so only regular unleaded but since then its all been premium, done about 2200 kays so far & the noise was the same with both fuels & is still the same now. Had the Holden mechanics listen & one of them drove around the back car yard but couldn't hear it, not much room to excellerate there though, need to go for a drive with them & try to see if they hear it then, its not that hard to hear if everything else is quiet.