Thanks HunterTodd, you made me check mine, but
Though I don't think I was having the noises that you were describing.
I have checked my air box (low fuel light on & 46K on odo) and found:-
* Missing screw from top cover of the air box (near sensor)
* Air filter very dirty.
* Oil (lightly) covering vent hole inlet area of air box.
* The two rear "trumpet mounts" that connect the trumpets (air inlets too carby), through the base of the air box AND too the top of the carb's, loose. I fitted a second washer (1.5mm thick) under the four mounting screws, problem solved.
* Checked "O" ring where the air box (top and bottom) joins together, and was there and OK.
Started engine and noticed no difference in sound/s (tested on centre stand)
So, happy hunting, and read with interest.