The engine of my 2016 LDV G10 is losing power and the engine light is on

First things first; have the car electronically scanned to see what fault codes are thrown up. From there you can make a much more accurate diagnosis of the problem. Simply replacing random sensors and other parts on a hunch is a fast way to throw money away and still be stuck with a car that doesn’t run properly.

The de-carbonising process you mention is sometimes necessary in modern turbo-diesels which, for reasons of emissions control, consume a percentage of their own exhaust gasses as well as any gas build-up inside the actual engine. And since the exhaust gasses contain soot, and the crankcase gasses contain oil, those two compounds get mixed up into a black, gooey paste that clogs the engine’s intake system. At this point it usually needs to be pulled apart and manually cleaned. If this is the case with your car, it could well be the cause of the check-engine light and the poor running.