For those flashed w/ occasional post cat CEL's
 

Ive had a few CEL's lately with 18k on the odo, most of miles with the EVOMS flash and Cargraphic exhaust. CEL was post cat, rich condition code, one bank or the other.

Could be many variables of course, most assume the cats are bad but having swapped the plugs out for new ones the CEL has not shown its face since.

So before your curse your exhaust manufacturer, or install the CEL eliminators might want to check your plugs, if flashed swap at 20k vs. what the manual tells ya.

I will report back if anything changes but so far so good, car runs much better also in the higher gears with plugs changed.

Did the plugs look bad? What plugs were you using and what plugs did you install?

Stock plugs replaced with stock, gapped per tuner recommendation. Did not inspect, dealer failed to return them even though I asked.

Whenever the full fuel charge isn't burned, you'll get that code. Almost always plugs, they simply can't burn the charge completely. Nothing to do with the cats at all, flash just accentuates the problem imo.

My car just has been throwing that code for the last 1K miles or so. No flash, only exhaust with 200 cell cats. Only 14,xxx on the odo. I can't imagine the plugs have gone bad already

Changing plugs did not help
 

Changed my plugs and still got CEL (error 420 / 430). My fix was to add a mini cat bung extension. Clever invention and it really works.

http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html

Your plugs are probably fine if not flashed.