Good day gents! - Thankful you're all here. This is such a helpful group and enjoy reading all the support on virtually every problem out there, ha!

I've got a 2011 F150 FX4 with the 5.0 coyote. Love the truck, factory ordered it and she's been a phenomenal truck. Today I'm writing because I cannot figure out why the old girl is throwing P0430 and P0420 codes. I just changed the plugs using OEM ford plugs - verified the correct ones. Easy swap, no need to gap but checked all before install and all were same and good. All plugs coming out looked good as well. Did not have any codes or problems, just regular maintenance for the swap. Completed the swap, test run and all was good.
Hit the highway for a trip out of town for work, figured I'd throw in a tank of premium, typically run regular but will throw some premium in when going for 6+ hour highway runs. Got an hour out of town, and while the truck ran fine, engine light came on. Stopped for a break, had a code reader with me, checked it and got P0430 & P0420 codes. googled and found other threads here indicating codes for the CAT's on both sides. puzzled, but figured it had to be the gas??
Reset the codes and continued driving, within another hour, light back on. Got to destination and had a lumpy idle, not in a bad way, but I could feel it - A/C was on, turned off, still noticeable, but less noticeable.
Checked the codes, same codes. Reset and drove to/from work for a few days, light was off, came back on, now only getting P0430 code - no P0420.
Finished the tank of fuel, filled up with regular Exxon and have continued driving for the last 10 days, some days are better than others. Can go 2 days with no code, then comes on again, only P0430.

Can anyone enlighten me what could be going on here? I understand there are several possibilities, but having never seen these codes before, and the sequence of just changing the plugs, and suddenly these codes show up has me puzzled. Could be a crazy coincidence but would like to think it's not the cat as both sides (0420/0430) originally showed up, now only one side consistently. Could be a sensor, but I'm thinking it had to be triggered by either the plugs or the fuel...any insights or suggestions would be greatly appreciated!!!

I'd really like to avoid taking it to a shop, especially one on the road, for them to try and throw parts at it or spend hours diagnosing something I can already know.

Thanks in advance gents. Following.

-SS
'11 F150 5.0
Alberta, Canada

 

Did you ever find an answer to the cause?

 

Download forscan and do a mode 6 test. Look at the cat efficiency and report back.