I recently did put in a helicoil for a snapped valve cover bolt, and afterwards I am getting sputtering at low rpms when accelerating...

Spark plugs looked good.

I noticed little oil in intake air box, so i drained oil and replaced pvc. Pvc had oil in tip and wasnt rattling, so seemed bad. However car is still sputtering after replacing.

Now I am thinking I may have missed some metal shavings while drilling for the helicoil and possibly clogged an oil passageway. The old oil filter did feel heavier than it normally would.

Any idea how I should continue diagnosing this issue? I was thinking of inspecting/cleaning oil passageways, but cant find oil flow diagram. TIA!