Skoda Rapid Diesel Engine Issue

That sounds awfully familiar! I had a similar issue with my old Renault Megane, also a diesel. Low pressure plus emission control usually points toward something in the exhaust system. Reduced power is limp mode, where the car limits engine output to protect itself. Have you checked the pressure sensor? That's what caused my problems.

Pressure sensor, huh? I'm not super familiar with that part. Is that something I can check myself, or am I better off just taking it to a mechanic?

Given the symptoms, the pressure sensor seems the likely culprit. It's responsible for monitoring the pressure in the exhaust. If it fails, the car can't properly manage the diesel exhaust, leading to reduced power and other issues. While you could try checking the sensor's wiring, honestly, for something like this affecting emission control, it's probably best to take it to a workshop. They'll have the tools to properly diagnose and replace the sensor.

Just got it back from the shop. It was indeed the exhaust back pressure sensor. New one installed, and the warning light is gone, power is back, and no more smoke! Cost me 245€, but totally worth it to get my Rapid back to normal.