I would only go OEM myself. There is a special electronics box that plugs into the wiring harness. This takes care of the light wiring and tells the traction control system that you have a trailer, which is supposed to adapt. I doubt the aftermarket system has such a thing. Anyway, is it worth the risk? Check this out:

http://www.x3world.com/articles/x3/b...h-2006-x3.html