C6 Boost Leak

Sounds like what happened with my C6. Check engine light, power loss, whistling and hissing all point to a boost leak. The electrical bypass valve is often the cause, and it hits performance and fuel economy hard. Have you checked all the hoses and connections to the turbocharger? A split or loose connection can do it.

Where exactly are those hoses and connections located? And how do I check them for damage? I want to take a good look and figure out what's wrong.

The hoses go from the turbocharger to the intercooler, then to the intake manifold. Look for cracks, splits, or loose clamps. Feel the hoses for soft spots or bulges, which means internal damage. Honestly, it's a complex system and easy to misdiagnose, so I'd suggest a workshop. But it does sound like my issue, which was the bypass valve.

Thanks for the advice. It really helped figure things out. I took it to a workshop, and you were right, the electrical bypass valve was the problem. The repair cost 250€, and it fixed everything. Thanks again.