Hmmmm, another snake oil question !!

The best turbo 'cleaner' would be decent quality fuel with good spec, low ash engine oil changed regularly. How any additive whether it be added to the tank or the intake effectively clean anything after being subjected to the pressure and heat of combustion ?

The old adage of 'rubbish in, rubbish out' applies to this. If poor quality fuel and oil is used in the first place there will always be problems on the exhaust side and, to my Knowledge, there has never been a 'wonder' product that will change this.

I don't have superior knowledge, I just have common sense.

All fuels have additives at source. Some are better than others at reducing soot / carbon but it's how efficiently the fuel burns that denotes how much the waste gasses leave. Using an additive that claims to clean downstream of the combustion chamber will make little difference to an engine that uses poorer quality fuels / oil. Sure you may see a small, short term boost to performance by the additive having an effect on the octane rating, but like drinking RedBull or any energy drink, once the effect wears off, it reverts back to normal.

Regular servicing with quality oils makes the biggest difference to engine performance / economy as it ensures the engine is kept clean in the first place. I've seen the insides of countless engines and their fuel / exhaust systems and it's always the better maintained ones that are the cleaner ones.