Is the 1999 E55 supposed to have 02 sensors before and after the pre-cats? My car had O2 sensors before the cats and adapters for the O2 sensor after the cat but no O2 sensors.
Is this normal? I have headers and the front cats were removed with the sensors being installed in the adapters that used to be after the cats. (does this make sense?). I am just a little concerned because all the references to exhaust systems on CLK's and E55's seem to talk about O2 sensors in both locations, not just the one.
Thanks