I feel your pain, had the same problem on a 650i, the cost of repair was fairly eye watering (quoted around £3k at BMW on car worth £6.5-7 tops), lots of labour involved, and from the look of it a fairly specialist job on such a complex engine. If you check the american forums you will see this is a very common problem on the N62 engines, certainly enough for me to not even consider another BMW with the N62, absolute pain that affects an otherwise superb piece of engineering, and goes some way to explain the number of V8 6s and 7s being offloaded on the cheap these days.

