p0420 code

[00civicb18c5]

ok i know what the code means (cat default below lower threshold) i have new exhaust from the header out, i just replaced the 02 sensors, the only problem besides the check engine light is on a cold start taking off i go a few hundred feet then it just doesnt want to move like the egr valve is stuck open. but there is no egr valve on my car. so im thinking a map sensor or something. it drives fine on the highway and its runing rich.