It's not the master, I know what that feels like (had to replace the one on the race car).

So it's either the vacuum pump or the booster. I'm going to order up the vacuum pump o-rings. I put my hand under the pump this morning and it is caked with black crud. I'm guessing there's a leak that needs fixing if nothing else...

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual