Thanks to everyone for all of the info and recommendations. We have since determined that it is the VVT that is making the noise and I’m going to put a “new” rebuilt engine in the car. Also, we are going to rebuild the timing section of the old engine and save it for a backup, or sell it outright. The new engine will be using synthetic, as that seems to be the consensus.
Many thanks to all.

 

When switching to a full synthetic it is recommended to change the oil and filter at 3K two times before moving to an extended interval. This makes sure any deposits knocked loose are removed. Also agree with previous posters, modern synthetic oils keep seals conditioned. However making sure your oil stays clean (Anything over 5K seems suspect, like a sealed for life transmission, BS.) is more important than conventional oil v synthetic.