Funny noise in higher power range - trying to dial motor in once and for all.

Yeah it's not vibes, it's super smooth on that note it's just , idk like I said it's hard to explain. I do have a 36t sprocket put up I've just been waiting to put it on. I almost think it's what they call 4 stroking at some points, sometimes it does it sometimes it doesn't. It just cuts power and does it for a sec then picks up. I've seen what the bike can do it can get way up there I'm sure 30 at least , I only have it officially at 27, it just won't do it all the time.
Does the exaust tone dip down to a lower tone when it does this?