The part in question is marked in blue
Thank you. As you have suggested, I looked at the throttle body for anything unusual, took out the intake manifold and coils and checked some of air hoses. I found the wire connectors to the ignition coils were pretty bad (damaged). I've changed the 2 worst ignition coil wire connectors. I've put the intake manifold and coils back and test drove it. The throttle response became very bad. I drove it hard hoping the throttle body will correct itself. The check engine light went away but "EPC" light remained.I have the same car & did same PCV valve change a year ago. The risk areas of CEL happening are mostly electronic. In my case the oil flooded one of the ignition coils, giving rise to ignition fault code, thorough cleaning fixed it. I have a proper VCDS to diagnose.
In your case, you are guided to borrow or find a proper scan tool. VCDS is minimum to give a more elaborate study.
Without that, a pointless wild goose chase....