At 135k at the very least the upper plenum did not look like this. It was a bit bronze looking but no black gunk. At 135k I had it opened up cleaned following items egr port, egr valve, throttle body. Replaced pcv valve then also with aftermarket valve. At around 150k changed pcv valve with oem valve. I believe the aftermarket pcv valve may have been faulty as when I took it off and shook it I didn’t hear a rattle. Soon after decided to change leaking front valve cover gasket and this is what I was greeted with.

 

Change the oil more often

 

I do.

 

heat