Hi Ian,
Just my opinion ofcourse but : Part of the secret.....
I suspect this is Canadian Snake Oil loosely based on science and a dose of solvent chemicals.
If the machine circulates the " magic liquid' through your cars fuel rail it removes the inevitable build up of crud and then they show you a glass jar of all the dirt removed from your engine
which was not doing any harm clinging to the pipes.
Any of the Fuel injector cleaners sold will do some degree of the same thing.
Run her down the motorway in 3rd gear for 10 minutes, that will blow out more carbon
I am not a mechanic either
Phil