I dunno HotGrbg, I've been chasing it for a couple of years on our 535xi. It leaves one code, 30FF. There are no other issues. I've replaced vacuum lines for the turbos and checked the linkages. All the dump valves operate properly and seal. 30FF is the code I see every time. I'll find it one of these days. It doesn't happen regularly enough to be a big issue as yet. I can allow a few hissy fits at almost 250,000 miles I guess.