Most of the time I talk with the mechanic on the phone, because they're not that consistent with email or returning messages...

But here are some quotes which therefore don't tell the whole story... joining the investigation halfway through, after chatting about what the problem could be, thoughts about possibly pulling the head to inspect/test, walnut shell blasting etc.,

Aug. 5: When trying initially to scope the valves, he sent this comment and photo:
"I can’t get close enough to see a valve without scraping stuff off the wall and blocking the camera"


Aug 5: "So. We heard the noise finally. When we were circling around possible sources, it stopped. We did a pretty gnarly intake cleaner (after the turbo, directly into the intake), let it soak, and then I went and really put the heat to it. We're going to let it cool down entirely and see if it makes another buzz for us. The noise seemed to be coming from top end or passenger side high on the engine. It could be phaser chatter, maybe chain tension, or a valve adjuster? Not sure. It needs to do it again for us. When we pull it back down for the cold noise inspection later, I'm going to try and re-scope the intake. Hopefully there was enough cleaning of the last two runners to get around the bend without getting covered with goo."

Aug 12: I asked if any progress on the scope/gunk or other diags...
"It certainly made a difference looking in there again, but to call it “clean” would be a stretch. I still hear something. I think it’s might be more mechanical than rough running. I’ll get it warmed up again and see what presents itself. "

No update for a couple of weeks, squeaky wheel... I asked again about compression/leak-down,
which they then did and said it passed, so after discussion they feel the issues are probably in the top end, but not sure exactly what it is.

 

Would those be noticeable at idle as well as under power?

 

They will find it when they tear down the top end. That much oil in a cylinder combustion chamber, I’m still thinking head gasket, rings, pvc system failure.