Got this code today going to town. I looked it up but don't understand what it means, i am guessing something to do with the O2 sensors. I have Pacesetter headers and a little leak at the collectors that I need to fix. Could that have anything to do with it?

 

No That Means Your Sensor Is Staying In The Middle.... Not Going Lean Or Rich.... So Basically Your Upstream O2 Is Crap.... I Believe It Is Bank1 Sensor 1

 

Should I just replace both of them or just the bad one? Any recommendations on which ones to get, part #'s, etc....