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      03-16-2014, 04:35 PM   #11
335DEE
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Drives: 335d
Join Date: Feb 2009
Location: England

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my 2p';s worth .. as had the same issue on our e39 530d , turns out it was vacuum hose had gone brittle and was leaking air in under full vacuum and thus not pulling the actuator back far enough so the turbo wasn't spooling up to it's proper speed .. hence the woooing / siren noise