Alphard Whistling Noise and Power Loss

I had a similar problem with my Alphard. Is it like a boost leak, maybe? Have you checked the pressure sensor or the turbo actuator itself?

Boost leak could be it, yeah. Where exactly did you have a look to find the issue? Did the turbo actuator look obviously broken?

I didn't dig too deep myself. Based on the symptoms, especially the whistling noise, and the error codes, it really sounded like the electrical bypass valve was defective. I recommend you take it to a workshop to have it checked properly.

Thanks a lot for the info! Took it to the shop and you were spot on, electrical bypass valve was indeed defective. They replaced it, cost me about 250€, and now it runs like new. Appreciate the help!