Seat Ateca Diesel Engine Problem

I have a Seat Ateca as well. Your symptoms sound awfully familiar to what I experienced a while back. Check engine light, loss of power, weird noises... It could very well be related to the turbocharger system. Have you checked the MAP sensor readings? A faulty MAP sensor can sometimes cause incorrect boost pressure readings, leading to similar issues. The whistling and hissing sounds suggest a potential leak in the intercooler or its hoses as well.

Interesting. Where exactly is the MAP sensor located, and how would I go about checking its readings? Also, concerning the intercooler, is there a simple way to inspect it for leaks, or is it best left to a professional?

The MAP sensor is typically located on the intake manifold. You'd need an OBD scanner to read its values while the engine is running. Compare the readings with the expected values for your engine. As for the intercooler, visually inspect the hoses for cracks or loose connections. You might hear a hissing sound near a leak while the engine is running. However, it's often difficult to pinpoint the exact location without specialized equipment, such as a smoke tester. Given the potential complexity and the symptoms you're experiencing, I would advise taking it to a workshop for proper diagnosis. It does indeed sound like a turbocharger issue, and if it is the wastegate valve, it will only get worse.

Thanks for the insight. Took it to the shop, and you were spot on. Wastegate valve was the culprit. Cost me 860€ to get it sorted.