O2's and headers..

[realcanuk]

I have just completed a new build and am sorting things out and will be looking for some help and advice.

I have read about headers giving problems with the O2's but can't seem to find a good description of the actual symptoms. I had the same headers last year without issue, but I had them coated and am wondering if maybe they run cooler and are giving issues now. I have checked everything I can think of
My 02's are working erratically. They will stop working after idling for a while, and if I run the engine rpm up a little they will start workiing after 15 or 20 seconds. If I leave it idle they go off again. This pattern is fairly consistant although sometimes they stop even with rpm higher.
Is it possible the coating of the headers is enough difference to give me issues ? Is there anything else I can check that can cause this behaviour ?

Thanks

[Iam Broke]

At idle my O2's still switch but it becomes very slow as they are so far downstream. I see the WB fluctuate from .96 to 1.03 lambda at idle but no codes set. If any do, I'll just turn the DTC's off. Not too many miles on the setup yet. LTFT's seem to swing a pretty wide range trying to compensate. Hopefully they will settle in once I quit fooling with the tune every drive.