Andrew - these are good points.

There was a similar sound before changing the chains, but now it's somewhat different.

I am using Motul 5W40 instead of the recommended 5W30 due to the crank wear being at the upped end of the tolerances. Level is 3/4 between min and max.

It does not happen at a cold start, probably not even at a warm start (after sitting for an hour or two). Only after the engine reaches normal temp.

Good point about the oil pump. When the engine was out, the pump was inspected and there ware no reported issues with it. It's actually quite a big unit this thing.

For these reasons I'm more inclined to think it could be a Valvetronic or air intake issue...?