2003 330xia- Is there any history on this type of problem(s)

I thought I'd put this out there to others who have the knowledge and the history of this engine.
These are the symptoms we are experiencing with our 330xi automatic (M54 B30
engine). I may actually be describing more than one problem?
1. engine starts fine when cold with the exception that 25-50% of the time I hear something like metal to metal rotary contact (problem# 1). I have read about the Double Vanos o-rings that are supposedly the wrong material but I find it hard to believe BMW hasn't corrected that in the 2003.
2. engine is difficult to start when warm (problem# 2). When hot it starts fine, it's only when sitting say 25-35 minutes in real cold weather or 40-50 minutes in warmer weather is it hard to start without touching the e-gas petal a bit.
3. there occasionally is a slight polymer odor when the car has been running hot. oring?, coolant? synthetic Mobil 1 engine oil? I am not sure.
4. I do want to mention this. Last fall I did attempt to replace all of the coolant before my maintenance manual had arrived. I opened the radiator removed the cap and bleed screw next to the cap and received what I thought was a less than full amount. Because the weather was turning bad I figured there must be another bleed screw and a partial change was better than nothing. So I topped off the radiator with what I believed was the equivalent of what I drained out. After driving the first time and the car cooling I checked the radiator and overflow. I think I had to add a little to the over flow but just that once. So now it's 4-5 months later and I noticed that the overflow has dropped approximately a 1/2 inch. I am thinking head gasket but shouldn't I be getting a lot of white exhaust at startup and/or chocolate milk engine oil?
This car has only 24,000 mi and has not been abused, I tend to drive fast but not rough (jerking the car around). We are the only owners, bought from a dealer, I believe it had some test drive miles on it, but we should have seen this earlier if damage was done from abusive test drives.
If anyone has any ideas or history with the double vanos, head gaskets, heated thermostat that may help, I would appreciate hearing about them.
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