You could be onto something, although 95 oct is regular in the UK and from the 1st tank full I started using Super which is 98 Oct, and I have not heard the noise since. But 95 is the equivalent to 87 AKI. But it could also be the engine is bedding in as its now done 2k miles. I will listen out for it and see if I hear it again.
I have heard this sound and I run NOTHING but Super Unleaded USA 93 Octane.
I heard it on my 15 RT and I hear it on my 17.5 GS.
It sounds just like ping or knock.
I cant get better then 93 octane at the pump so not sure how I could proof it out. I could try to mix AV gas and 93 pump gas.
It sure isn't from me lugging because that is the last thing I can be accused of. I run the RPM'S up and try to keep them there so that is not the answer.
Of course you have such a noisy motor, fuel pump, ABS unit, Injectors and tires, with so many other noise producing sounds to go through it is hard. And of course you do not hear it at speed as it is overcome by over all sound.
Not sure what it is but I hear it also. And that is through costume molded ear plugs with a -15 DB cut through all ranges.
Noel is not crazy, and his hearing is fine. This is a "thing".