Noises are a pain to locate sometimes.... I had a loud ticking noise above 50 mph that was driving me nutzo, turned out to be the visor on my helmet vibrating against the snaps.
Do you still have the AI installed? The reed valve makes a high pitched noise at speed.
Maybe it's an intake noise - check the clamps on the rubber tubes on the front and rear of both carbs.
It could also be the chain. Chains sometimes make noise under load at speed.
Find a road with a divider barrier and ride next to it. Or an alley. It may help you locate the general area where the sound is coming from.
