i'm curious how the header would be bad or how they determine that it was bad?

I might be having the same symptom. On some morning, cold start (car sat overnight), it would idle kind of funny. The RPM doesn't pulsate but I can feel the car pulsating for a few minutes. It would go away however.

I have a 07 s2k with 90k on it.

what mod did you have? do you have flashpro?

did you notice your mpg gone done since it happen?

 

I don't know. Honda replaced the head with the exhaust valves plus a couple of gaskets. Oh well. At least I have new parts

 

I meant head, not header ******