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At 164 k miles, I would run a tihcker oil, like 10w40.
You could also add some PTFE treatment like Nulon E10 or E20.
The first thing to do is remove the breather hoses from the engine and inspect for oil residue, and inside the air inlet duct to the throttle body.
Can you do these little checks and come back with your findings?
Do you need any further help?
I hope my advice has been of assistance to you.