MZ/MuZ Riders

Ive been trying to find this annoying noise, it sounded like valves out of adjustment. BUT all clearances are checked at last service. I dont have the airbox snorkel fitted, would this contribute to the noise? It seems at around 4500 rpm in top and about 110kph that it gets noisy. It doesnt detract from the riding apart from the annoying rattle.
Ive checked all fairing bolts, headlight mounts and instrument cluster...