Vivaro sudden loss of power?

While driving my vivaro home up the m6 just south of Brum my 05 82000 van suddenly began to lose power no miss fire or anything just lost power after eventually pulling into the hard shoulder thinking fiuel problems the engine was still running but with a strange buzzing sound comming from a little valve type devise on the right hand side of the engine compartment not sure what this devise is but it has a round top and two small rubber pies going when i removed the pipe the buzzing stoped thik it may have something to do with the turbo any way limped of the motorway and limped home back road van will do about 50 mph easily up th fith gear but seriously lacks power and dies in sixth or up a hill any ideas Thanks