V70 Exhaust Leak and Catalyst Error

The exhaust leak is likely the problem. It can introduce extra air, mess with the oxygen sensor readings, and reduce the NOx catalyst's efficiency. Any idea where the leak might be?

Not sure where the leak is. I checked, but couldn't find it. Since the error is about the NOx storage catalyst, could the leak be near it, like at a joint? Should I check the lambda probe?

The leak could be near the catalyst, but they can be hard to trace. Given the error and the car's age and mileage (111054 km), get a smoke test to find the leak. That'll give you a better idea of what's up. Only check the lambda probe after you've confirmed the exhaust system is airtight.

Thanks, I'll get a smoke test done by a mechanic and then fix whatever needs fixing. I'll let you know what happens. The final cost was 265€.