So my a4 had a small head gasket leak where it would burn coolant and leaked coolant through the rings into the crankcase to make diarrhea oil. It had a po303. I tried the bars head gasket fix and it seemed to work since im not losing coolant but now i have the po300-303 and also a po135 o2 sensor heater circuit.

did burning some of the bars leak before it sealed the gasket ruin my o2 sensor? Or did the coolant burning finally ruin the precat on that bank? The car will barley run now and cuts out like crazy when giving it gas. Any ideas? Thanks.