Insignia Diesel Particulate Filter Issue

That does sound concerning. I had a similar experience with my old Volvo, though a different model. Reduced power and smoke, you say? Did the engine light come on? Also, have you noticed any unusual smells or noises coming from the exhaust system? A sensor fault could also trigger similar symptoms.

Yes, the engine light is on. I haven’t paid attention to any specific smells or noises except for the louder exhaust due to the smoke. Could a faulty sensor really cause this much of a performance problem and exhaust smoke, or am I really looking at a DPF issue?

With those symptoms and the engine light, it's highly likely the DPF. The sensor could contribute, but the smoke especially points to a filter issue. Cleaning might help in the short term, but replacing it could be unavoidable long term. I ended up having to replace the DPF on my Volvo. Best to get it properly diagnosed at a reputable workshop.

Thank you for the helpful advice and for sharing your experience. I took it to a workshop, and you were right – the diesel particulate filter was indeed defective and had to be replaced in the end. The overall repair cost was 1550€. Now the car is running smoothly again.