Hi I have the same car with approx the same Miles ( 170.000 Km) mine do the same sometimes just when cold and for few seconds (max 15s).
Never when hot, in my opinion are just the hidraulic lifters and i am not sure about carbon in heads.........if the car was mine i never take down heads for this if i ma not sure........this is a big job.
With the new fresh oil the situation is really better .
Alberto