Providing an update here after a couple weeks of diagnosis. Making some progress but haven't fully resolved these issues.
On Issue #1: I suspected this to be hydraulic lifter noise so I did an engine flush/oil change. No immediate results after this (to be expected). However, I added some
Liquid Moly Hydraulic lifter additive after the oil change and the lifter noise almost immediately went away. I'll report back after a few weeks of driving, but turns out this stuff may not be snake oil...
On Issue #2: Even though I had just replaced the AOS about 2 years ago I went ahead and did it again and replace the oil fill cap to try to rule out crankcase ventilation issues. The noise has not changed at all, so I think my next step is to smoke test the intake to see if there are any leaks there. I don't have a smoke machine, so going to have to see if I can find/borrow one.
If anyone has experience with common intake/vacuum leaks and how to diagnose, I'm all ears.
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