As the original poster in this particular thread, I can report that I have had no further occurrences (engine light, reduced power). But as a superstitious person, now that I have typed that...well, we'll see!
My only niggle at this point on my X1 is that the trunk release on the remote is so finicky that I basically have given up on it. You have to lift anyway so I just grab it with the key in my pocket and it comes up. But if I press the trunk release for one second, nothing happens, and if I press longer, the panic alarm comes on. Super annoying, so I avoid the trunk release.
Oops think I just hijacked my own thread...