theres gotta be quality plastic covers out there that can last a lifetime under extreme heat. I doubt there is industrial/aero quality Stuff lasting less than a decade being used in airplanes and so onThat's part of the branch of the engine wiring harness. I think that goes to the idle actuators. I see this in my other 08s too. The plastic on the hard shell connectors are made of chocate. This is why I'm redoing all the insulation on my engine wire harness. This is from my project engine.
BTW the conduit is all made in germany by Schlemmer, BMW has mandates to make their cars more environmentally friendly so the plastic breaks down faster. That's great for selling more parts and cars, but we'd all be better off if that conduit was made in mexico or china...it wouldn't self destruct.