I've had a couple mystery problems on my 2000 540i that I haven't been able to figure out yet; hopefully someone here might know what they are. The first is white smoke on startup. It happens fairly regularly, but very inconsistently, with no discernable correlation with the amount of time the car has been sitting and whether or not it smokes. It rarely smokes first thing in the morning, never smokes if it's been sitting a couple minutes, but almost always smokes when I start it up after work. My mechanic suspects the valve guide seals. The PCV has been replaced, and the smoke did not go away. The second is a creaking sound at low speeds. It can be heard/felt inside the car while rolling at a couple mph (like through a parking lot), but cannot be heard from outside the car. This is also not regular - it doesn't happen all the time, maybe 1-2 times a week. It goes away upon acceleration. Thoughts?