Most of the codes "reducing" look related to the fault of blown fuse. Are you blowing fuses when you replace it? First try that before you start unplugging things.

Injector code and irregular rotation could be a bad injector, there's been a problem with the x5 having leaky plastic at the passenger side, which drips onto the engine cover and corrodes the injector(s) 5 and/or 6. I had to replace both and yes the car stumbled and stalled at times because of this. IMO remove the engine cover and the foam and don't put them back. I can't find the thread right now on the plastic engine cover repair, but I will post it later if I find it.