Modus Air Intake Leak

Sounds like a classic air intake leak. The hissing under acceleration is a big clue. Check the intake hose between the air filter and the intake manifold, especially after the MAF sensor if you have one. Cracks are common. Any recent work on the turbocharger?

Thanks! I'll check the intake hose. If it is leaking, could I tape it up temporarily, or does it need replacing? I haven't touched the turbocharger. Not sure about the MAF sensor, where would I find that?

Tape is a very temporary fix, it'll probably fail quickly with the heat and pressure. You'll need a proper replacement to avoid unmetered air messing with your engine management. The MAF (Mass Airflow) sensor is usually right after the air filter box, inline with the intake. If it's after the leak, that could cause issues too. Honestly, with those symptoms, it's probably best to get it checked professionally.

Thanks for the advice! Took it to a local workshop, and you were right, it was a leaking intake hose. Cost me about 100€, including the new hose. Fuel consumption is back to normal, the hissing is gone, and the check engine light is off. Thanks again for pointing me in the right direction!