Do you have any practical joker mates? The harmonica, cable tied before the radiator is a funny one, not that this is what your issue is.. You'd know that one, it sounds like a dying donkey when you get up to speed on the road, but that sounds like an air leak under boost??
That or some smart arse has stuck a mouth piece from a recorder/flute in your air box or down your snorkel... does your snorkel have the inlet that you can slide a beer can down, thats a p.t.a one lol.
I had mates that thought it was hilarious to do that one, the first thing i did when I built mine was to net the inlet on the snorkel.. I've been got by the cable tie on the tailshaft!
Sounds like a hose split at the hose clamp, grab a spray bottle with soapy water and wet the hoses, see if any bubbles pop up!
As Tony wrote, it may show traces of it with out it.. I'm betting it's a pin hole or you'd hear it under lower revs???
Highly suggest the cable tie on the tailshaft, you need the real big heavy cable ties! Your mates will love you for it