Auris gasoline turbo issue

Sounds familiar! I've got an Auris gasoline too, and had similar symptoms a while back – the hissing noise especially rings a bell. Have you checked the MAP sensor? That can cause boost pressure problems. Reduced power and whistling sounds like a turbo issue for sure though. Does it happen at all RPM ranges?

Thanks for the quick reply! I haven't checked the MAP sensor yet, but I will. As for the RPM range, the hissing is mostly noticeable when accelerating, especially at lower RPMs. Above 3000 it seems to smooth out a bit, but the power is still not what it used to be. What was your issue, exactly?

Okay, so mine turned out to be a faulty wastegate valve in the turbo. The hissing was the boost leaking out. If it's mostly at lower RPMs, that points even more to boost control issues. Honestly, diagnosing turbo problems without the right tools is tricky. I'd recommend getting it checked out by a workshop. They'll be able to properly test the boost pressure and pinpoint the problem. Cost me about 860€ to get it sorted.

Wastegate valve... noted! Thanks a lot for the insight. I'll take it to a mechanic and have them check the turbo and wastegate specifically. Hopefully, it's just that and nothing more! I will post what I find.