Peugeot 607 boost pressure fault

Sounds like a pain! Boost pressure issues can be tricky. First things first, have you checked for any obvious leaks in the intake manifold or any damaged vacuum lines? A pressure drop could definitely cause those symptoms. Also, when was the last time you checked the pressure sensor? A faulty sensor could be sending incorrect readings to the ECU, messing with the boost control.

Good shout on the pressure sensor! Where exactly is that located on the 607? And regarding the vacuum lines, is there a common one that tends to crack or fail on these engines? I'm trying to avoid tearing everything apart.

Okay, so the pressure sensor is usually mounted on the intake manifold somewhere, follow the pipework from the turbo and you should find it. As for the vacuum lines, pay special attention to the one that runs to the boost controller (if it uses one) or the turbo actuator. They get brittle with age and heat. Honestly, with those symptoms, and without proper diagnostic tools, you might be better off taking it to a workshop. They can properly diagnose it and save you a lot of time and frustration.

You were spot on! Took it to the shop, and it turned out to be a defective vacuum switching valve controlling the boost. New valve, and she's running like a dream again. Total cost was 140€ Thanks a bunch for pointing me in the right direction!