The engine whine is more than likely a side effect of the cassette adapter. I do not have a cassette deck in this vehicle, but I had bad engine whine when using the cassette on my previous setup. So bad I refused to use it. I am thinking the DICE is in order...

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2004 BMW X5 3.0i - Mine
2011 BMW 328i xDrive - Hers
2002 BMW 325xi - waiting for a new owner