I'm defintely not aware of anything X5 related. Which engine do you have? Usually it's not that hard a problem, but im used to them on e34's and e36's. It's really not that difficult to change. I say, buy yourself the O2 sensors, and get your shop tp put it on a lift adn let them change it for a few bucks. Sorry I just dont know where yours are. Might be under certain cylinders or might be along your midpipe.