RCZ check engine light and exhaust smell

Sounds like you might have an exhaust treatment malfunction. I had similar issues with my old Volvo V70 - check engine light, rough running, the works. It turned out to be a faulty lambda sensor. Have you checked that?

Lambda sensor? Where is that located and how would I check it?

It's usually located in the exhaust pipe, before or after the catalytic converter. Honestly, unless you know your way around engines, I'd suggest getting it checked at a reputable workshop. It could be a particulate filter issue or even EGR valve as well, but the symptoms do align with lambda sensor failure.

Thanks, I appreciate the advice. Took it to the workshop, and it was indeed a defective lambda sensor. Cost me 375€ to repair.