ok, this is better - 2003 E53 3.0 inline six. no wonder it looked so familiar - i thought it looked like the E34, actually it looked like my old E39...

I have V8s so i can't help you directly but if you have a "zoom-out" pics, it might be helpful - don't forget, this is a remote diagnosis, which is not that easy...

other helpful things for you to share with us - what happened first - the codes came up and then you did all the changes to the spark plugs, gaskets, etc...? or, you did the changes and then the codes came up? We need to understand what may have caused the issue in the first place - what is the current mileage, and under what conditions the car is driven? agressive? mild? highway? in town errands?