Seat Alhambra Idle and Stalling Issues

Sounds like you might have a vacuum leak somewhere. I had similar idle problems and engine stalling in my old Renault Megane. The check engine light was always on. Have you checked all the vacuum hoses? It could be something simple like a cracked or disconnected hose.

Interesting. Where should I start looking for these vacuum hoses? Are there any specific areas that are more prone to leaks?

Definitely check all the vacuum hoses. On my Megane, it was a small, almost hidden hose near the air valve. It had a tiny crack causing a vacuum leak. Given your symptoms, it's worth a thorough check. If you're not comfortable doing it yourself, a mechanic should be able to diagnose it pretty quickly.

Took it to the workshop as suggested. You were spot on, it was a defective hose connection to the air valve. New hose fitted and now it runs like a dream. Cost me 175€ all in. Thanks for your help!