I had a shop install a rear sway bar on my xdrive at $100/hour but they discovered it didn't fit when it came time to reconnect the subframe. Super embarrassing seeing as how they were going out of their way for me, but the catalog had marked it wrong - it was by Megan racing. After taking to them they discovered they don't make a rear sway for an xdrive, even though they clearly advertised one. They refunded and I sold the bar to a rwd owner.
these look sick
https://carbahnautoworks.com/product...435i-440i-rwd/