2007 Galant ES throwing O2 error codes
 

While out of town, the "Service Engine Soon" came on abruptly at 165K on the odometer. Stopped by an Advanced we came across, the manager hurriedly mentioned a few P codes referencing the O2 sensors, I assume the upstream as he then proceeded to tell me he once had an Eclipse that he continually had issues with the catalytic/header combo, suggesting this may be the root issue.


I've priced these at $400+, but the manager of the Advanced says even if replaced, they're just a design flaw of Mitsubishi's, that he had a custom header made. I wanted to get some advice before proceeding.


I did notice a degradation of course in fuel economy, also a slight "pulsing" of the fuel intake while climbing in the mountains of SE Tennessee/NW Georgia.