I can only agree to this video. I had it done myself on my Toyota auris 1.4 d4d and can only say the acceleration was improved as well as the idle as well as the lower noise volume from within the motor.
Why would you stick the sensor in different exhaust pipe on those two runs? Just why? I am not saying it changed the reading, but try to keep all the variables constant with these kinds of tests..
Owen a Skoda Octavia 2005 1.9 tdi pd with 280k miles, on mot test i got 2.7 reading (smoke) pass as the maximu is 3. Next day i drive on motorway a bit faster and change the gears on 3.5-4k rpm and surprise. I got 0.9 reading... It may be something which this carbon cleaning but i don't trust it. My experience, you decide 😊. Cheers 🥂
For what it's worth I drive at least annually across Europe. Usually with smaller diesels. But I've done it also with petrol cars. Typically it's about ~3000 km to each side. So 6000km total. I rarely "beat up" the engines but of course, it's driven on motorways, at motorways speeds. For a longer period of time. What is catching from this experience is that ALL engines. By the end of the ordeal are absolutely clean and "beautiful". Exhaust tips also become clean to the metal. Where before they are black with soot. Simultaneously the engines run smooooth! Nevertheless in about a week or two it's back to "normal". The smoothness vanish.
