Hey everyone, So I recently took my car to BMW for a new o2 sensor. Since then my AFR's have been nothing but lean. Everytime I get near the gas sometimes even just idling I've seen 20:1 but the car has no symptoms and if it wasn't for my jb4 I wouldn't even know. I been waiting for it to throw a code but it's been two weeks now and nothing. The car targets boosts and holds boost fine with no codes even after racing and beating another tuned 335i which I didnt expect. I did take the car back to BMW and asked them check the car. They said everything was ok but I could use a walnut blast which they were only going to charge me $1000 for lol. I obviously declined that paid my 220 for diagnostics and left a little discouraged. Anyone have any ideas what this could be besides oxygen sensors and is there anyway to test O2 sensors?