Idle rev go up and down continuously

What scanner are you using to check for trouble codes? Does the scanner read live data? If so, what are the short-term and long-term fuel trims?

An engine that revs up and down during idle sounds like a vacuum leak to me. The P0171 code confirms that the engine is running lean.

My guess is a problem when you cleaned the EGR system a couple of months ago. Did you use new gaskets between the intake manifold and the cylinder head and also between the EGR pipe and intake manifold when you put it back together?

Did you clean the EGR cooler. The P0401 code indicates insufficient flow through the EGR circuit.

 

Crappy oil change places are sometimes the last place people drive their car before its ruined. Just helped walk a friend through a major clean and high voltage battery recharge with too much oil in his Prius. So infuriating!

In my research to help him I learned that these untrained workers often inspect the air filter for an upsell and fail to put the cover back on correctly, which can cause these symptoms.

I also worked on 2006 Prius a while back that had these symptoms with a different error code and the fix was replacing the throttle body because the throttle body position sensor had failed.