Anyone have O2 issues after new headers?

[fireguy12117]

I put a rebuilt motor together last year and this past summer ive been getting a CEL that for the last couple times i ran the codes came up as rich codes on the O2 sensors. Its a rebuilt motor with almost new everything for sensors, fuel management...while i was at it i threw some hedman headers on. Could the headers be causing higher flow, throwing the O2 readings off?

I've not seen anyone posting up on this, its a bit of a mystery as the light will come and go on its own. just today it turned on at cruising 45mph speeds after warm-up and into closed loop, but i romped on the truck on the highway some for a couple miles, exited, and noticed the light was off and stayed off for the few miles home.

truck seems to run really well otherwise...

ive concluded no vacuum leaks as this pattern repeated for 3,500 miles to the east coast and back this summer, plus i've ran a vacuum gauge and had solid readings. otherwise, i cant understand why im getting rich codes.

 

[azhrei]

actually my wire broke to my o2 sensor before I removed them and emissions light never came on. I didn't bother replacing it when I installed the headers and got rid of the cats...