BPY cold start noise

[clockwise33]

After a decade plus of positive experience with my 06 GTI I decided to pick up another BPY in a 08 A3 DSG to use as a daily. I've gone through the car and it's been great for about a year. The only nagging issue I can't resolve is a loud buzzing sound at start up when the temp is below about 60 degrees. The sound is coming from the area of the PCV and or thermostat. I have replaced PCV, thermostat and starter. I've eliminated the alternator and AC compressor by starting w/o accessory belt.

Any ideas?

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