Whining from engine on the motorways

[Frosties]

As above ive noticed a high pitched whining sound on the mororway (not really around town) in time with the engine speed, it shuts off if i chop the throttle or pull the clutch in? I have recently put the baffle back in the end can so im hoping its just normal engine noise that im not used to hearing as apose to gearbox or Camchain ?

Have you tried changing up to 2nd  :look