Check carefully for any vacuum leaks. These K&N oiled filters are very messy and can contaminate the MAF sensor when improperly oiled. But inefficient catalyst codes involve BOTH pre-cat and post-cat o2 sensors as well as the catalyst itself. You can experiment around and see whether the intake is affecting both o2 sensor voltages. Upstream o2 sensor should fluctuate around 0.9 volts and the downstream should be a steady 0.45 volts. Now with that in mind, air intakes usually cause rich, lean, and MAF circuit codes...not inefficient catalyst codes (I have tons of experience with aftermarket intakes and have never experienced this code). I would just take a look at the o2 sensor voltages first. IF the downstream one is not 0.45 volts but the upstream is fine, then either the catalyst is failing or the downstream sensor is going bad. IF the upstream one is not around 0.9 volts but the downstream is at 0.45 volts, then: 1) your intake is most likely altering the air fuel ratio by too much, 2) MAF needs to be cleaned, or 3) o2 sensor is bad. Please experiment around and look at the live data for each sensor to make sure they are all working properly before replacing stuff. Hope this gives you a good idea on what to do.

sure can.

the K&N might have fouled up the MAF sensor too.