I have a 2002 ex 2.3 and i keep getting an engine code for CATALYST FLOW BELOW THRESHOLD. I had the cat replaced before the light came on because you could hear the guts of the cat banging around when you pressed the throttle. after it was replaced i got the code for the first time. i replaced the o2 sensor thinking that was it. it went off for about a week and then it was back on. gas mileage i also put got bad. i put on an aem v2 and it got worse still. does anyone have any ideas what the problem could be? it's driving me nuts. sorry for this being so long.

 

Which o2 did you have replaced, before or after the cat?
Also, when they replaced the cat, did they check for loose cat core nuggets in the exhaust pipe and muffler, after the cat? Can you still hear stuff banging aroud in the exhaust once in a while?