While the I6 and V8 (and even the V8 has different types), most people describe VANOS problems as jerky, loss of power, etc. This site is unrelatable to us, but read up on www.drvanos.com and or Beisan Systems as I bet their symptoms are similar to what you're experiencing.

If it's in fact the VANOS solenoids, that's exactly what you're hearing...oil starvation. There are check valves in there that are supposed to stop backflow, but apparently they fail and or the seals don't do their job. I personally run 0w40 and on maybe 3 occasions total I've heard a startup rattle, and that usually happened after the X has sat for at least a week or so and/or the rare occasion it sat overnight outside in the cold (visiting family in Reno winters), which makes some sense since seals shrink up in the cold.

The seals can be replaced, but as far as I know, BMW hasn't changed the gasket material, so eventually it'll happen again. I've tried contacting both sites above in regards to V8 kits, but neither has produced anything as of yet.

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