Does anyone have experience of 'regular' use of fuel additives in helping egr/intake manifolds etc clean?

Ive seen a few youtube videos (of smoke coming from exhaust which is supposidly crap being cleaned from inside engine systems)and manufacturer claims of what these things do but unless one has seen a pre-post of say the valves or egr valve...one may just have to take the manufacturers word.

My take is that if you pour crap in with the fuel then expect exhaust to be smokie lookingjust as if engine is burning oil. Nothing to say its actually crap being cleaned and released from inside engine fuel/exhaust system.