The cat and pre-cats on my 380sl are undoubtedly plugged up because the car has been burning oil, and the law requires the car to have a cat but not the pre-cats. So, I was thinking about reaming the pre-cats out to let the system breathe better, until I can get enough money together to replace the whole system with a stainless steel one.

Before I do, however, I was wondering if reaming the pre-cats out would negatively affect the way the car runs by, say, increasing the CO the O2 sensor sees, thereby, causing the sensor to alter its output to the Idle Control Unit?

In addition, I was wondering from a strictly hypothetical perspective whether reaming out the cat on a car with a cat that's downstream from its O2 sensor would affect the sensor's output the same way reaming out upstream pre-cats would?

Thanks in advance for any insight anyone can give me on this.