Today I received an email from vittorazi regarding my exhaust,
For what concern the silencer, I inform you that it is nothing dangerous or worrying. I'm sorry it's not aesthetically beautiful but he colour is due to the leak of exhaust gases inside the silencer where there is silicone.
Nothing changes in terms of performance or noise. Only the colour changes because the exhaust gases come into contact with the anodization and cause the silencer to change colour.
After the first versions we changed the way of assembly in addition to the silicone inside the silencer. In fact, this no longer occurs.“
So, it is not dangerous and there is nothing wrong with the engine.
So that's that, on a brighter note, skymax are sending me the service parts to address the mandatory service bulletins and bring my motor up to date, so all's well that ends well