Strange Noise on revving

[ronboy109]

Hey folks I am having a bit of an issue with my w211 (2009 OM 642), I am getting a very strange whirring noise on revving from the front of the engine (left side), seeming to come from the vacuum pump area or the inlet manifold on the inlet manifold there is a "unit" that has boost gauge attached to it and the whirring, may be coming from there)

I've lost my stethoscope so I cant quite work out the origination.

Any thoughts?

 

[Tonygw]

idler pulley? alternator? difficult to tell without a sounds clip

 

[SteveFromAvantgarde]

Usually the air intake baffle breaks apart inside. (The bit that connects the charge pipe to the lower intercooler pipe)