Max
Getting that code means its probably just under acceptible emissions, chances are still some catylist material left inside around the outside.

When it goes into limp mode you will know it.
Ive spit the guts out of a few h/f cats.
Went to Magnaflow exh instead of a chambered muff so it will shoot out my side exit & not clog the muff (or have rattle in muff if it doesnt clogg)
Gets excessively loud then minute later CEL came on & it lost all power.
Pulled over, reseet the pcm, fired up had noticeably more power & the CEL never returned.
Various model years react differently so its a crap shoot.
May get away with just a reset or have a code come up now & then.
May have to use the non fouler or sim.