I have 07 F350 6.0 never heard this out of any of my 6.0s. it's almost a whine but can hear it w turbo and out of empty exhaust. Almost like a supercharger noise stumped almost leaning towards actuator for turbo? Noise got real loud swapped turbos used same actuator noise is there but much quieter.

 

Any chance you could post a video of the noise?