read article below for symptoms of plugged cats and if there plugged you might need to check air pump, air valves and hoses that supplies air to the cats...prolly not working properly...
When I plugged mine I had no power. Soon I blew some vacuum lines off because the exhaust had no where to go. melted the vacuum line to the MAPS sensor. then my engine computer went into limp mode and flooded the heck ot of the car. Couldn' drive the thing.
Symptoms of a clogged cat: Lack of playful activity, sulking, reduced food intake, and no fecal matter found in litterbox.
Sometimes plugged cats will heat up enough to glow red, and there will definitely be a notable loss of power. You might also notice a funky smell coming from the exhaust/tailpipes. Go WOT a few times at night, then take a quick peek under there while it's still running. Also, pop the hood and take a look down from the top, if you're running the stock H-pipe with four cats, so you can see the top two that aren't easily visible from the underside.