Noise from Turbo?

I'm doing about 50mph on a slip road joining a main road, it's clear so I put my foot down (more) and the engine noise increases (roars) for not much extra speed. Off the gas and it settles back to normal.

I thought at first it was the clutch slipping. It's hard to tell but I don't think the engine is revving (I don't have a tach). I can only make it happen at speed on an uphill section etc, where the engine would be at maximum power. Could this be a noise from the turbo?

The clutch and everything else seems perfectly normal at lower speeds.
???

hi redwonton, i had a similar problem with my 300tdi & believe me the thing used to squeal. Traced it to a split turbo hose, replaced the hose & noticed the difference straight away.