2002 330i 63k miles

Time to fix the O2 sensor issue fellows, and I need your help!!! If you recall, I had to replace the valve cover gasket a while back because of leaking, maybe 6 months ago. One of the "sharpies" on this MB noted that I should have not used the red gasket sealer. He wrote there is a special gasket sealer for cars with O2 sensors. He was right.

When I went to start the car after the valve cover job, the car ran very rough for about half a minute. Coincidentally the original battery failed just while sitting in the garage for the couple days I did the valve cover job. I thought replacing the battery caused everything to "re-adapt" hence the rough running for about half a minute. Maybe not... maybe it was the gasket sealer (Permatex High Temp Red RTV Silicone gasket maker) that screwed up the O2 sensor/sensors???

The "check engine soon" light came on right after doing the valve cover job. It had never come on before. At first it was intermittent with no particular pattern, always different, a couple days it did not light at all. But it pretty much came on every day for most of the driving time.

I ran my code reader back then and only these 2 codes came up in this order: E4=Adaptation Limit cyl. 4-6, E-3=O2 Adaptation Limit cyl.1-3. Only those 2 codes for a couple months.

NOW... the light is staying on full time, and the engine seems slightly rough at idle. Time to fix this problem. So tonight I ran the codes and got the same E-4 and E3, -but also got a C-6 code-= Cat Efficiency cyl. 1-3. And all 6 codes for all 6 cylinders misfiring.

So gentlemen... where do I start? Which O2 Sensors should I replace? As always, thank you very much!