Adding fuel like crazy on bank 2 only suggests O₂ out of whack or injector not putting out.

You said you removed cleaned replaced injectors? Did you swap locations? I would swap 5 and 2 (center each bank).

What scanner are you using? Can you watch the smooth running live data to see what's going on with 5 before it's cut off?

Front O₂ are identical you can swap those. For some tests you can swap the connectors just mark correct position to get them back when done.

If the O₂ is reporting the wrong air mix you should quickly see the fuel trim go max on "bank one" if you swap the pre cat sensors or connectors.

Is there oil on the O₂ wiring? O₂ sensors get their atmospheric O₂ reference through the cable going in and head cover leak can easily get enough oil on the wiring to throw off the reading.

The DME is convinced the engine is lean and is adding tons of fuel.

If it adds enough fuel it will misfire. Maybe the center cylinder has an easier path to suck in that too rich fuel mix so it gets the misfire.

I didn't know about the 26% when I suggested CKP. Def need to solve that bank crazy lean first.

I would swap the pre cat connectors and if the error moves to bank one means O₂ bank two is defective.

To confirm unless it's also covered in oil I'd swap the two pre cat O₂ put the connectors back and see if the lean follows to bank one.

The good news is you have an extreme case of repeatable error you will find the source.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)