E90, cool to see that you got that set replaced. I can understand how if that sound was loud enough it would drive you bonkers. Also, "told ya" suffices on there not really being anything wrong
The bearings just get noisy on some of the turbos particularly after you spin them up high enough. Almost every tuned 335 I've been in had some siren noise at low rpm and throttle when cold.
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23 iX M60, 24 GT3 RS Weissach, 22 Rivian R1T, 23 RS3, 13 E92 M3 Competition: Akra Evo, KW V3, etc