The check engine light coming on after the installation of headers is disturbing to me and tells me that the great computer does not like the new catalytics on the new headers. I would not be afraid of any harm to the motor as long as the air fuel ration is close. But I hate dealing with a check engine light coming on.
I want to do this mod, but I do not want to fight a check engine light every two days. There has to be a fix for this somewhere.
Best of Luck
The guy did this three years ago...
Aside from that...
The fix is to set the codes to "No Error Reported" or switch the O2s off in the tune. Rear O2s have no effect on driveability. They only measure for converter function. High flow cats will not be as efficient as OEM cats and therefore will set the code. It does not effect the engine or how the car drives.