08 KIA optima code p2191 how to start diagnosing cause, should I change filter?

Question

System to lean at higher load bank 1what do I do first? Should I start by changing the filter before testing sensors and how do I test the sensor?

Answer 1

P2191 System too lean

P2191 for the Kia can also represent a rich condition as well as lean, first step is inspect for any vacuum leak at the PCV system . and if there is any exhaust leak prior to the 02 sensor, which can set this code ondition