Tourneo Boost Pressure Issue

Whistling and hissing point to a boost leak somewhere. Have you checked the intercooler pipes or any of the vacuum lines connected to the turbocharger? Could be a split hose or a loose connection. Does it feel like turbo lag is worse than usual?

Intercooler pipes and vacuum lines, huh? I'll have a look, but honestly, I wouldn't know a turbocharger from a throttle body! Is there anything specific I should be looking for on those pipes and lines? Like, obvious cracks or something? And yeah, the turbo lag is definitely worse. It's like waiting for a bus that never comes!

Okay, yeah, look for splits, cracks, or even if a hose has just come loose. If the turbo lag is really bad and you're hearing those noises, plus the stalling... it really does sound like a wastegate issue and you might want to just get someone to take a look. It's better to be safe than sorry with these diesel engines. My money is on a defect in the wastegate valve given you checked obvious things, and they're saying it's gonna be, like, 860€ so brace yourself.

Wastegate valve, huh? Sounds expensive! Thanks for the heads-up; looks like a trip to the workshop is in order. At least now I have some idea of what they're talking about when they try to bamboozle me with jargon. I'll let you know what they say!