Thanks for all the replies. I looked at the service bulletin and I'm pretty sure my issue was unrelated -- but another thing I will make sure to have checked out! The noise I had was definitely coming from the supercharger itself. I put a stethoscope up to it and the grinding noise sounded like someone dragging a suitcase across asphalt.

John

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04 C230K Sedan
01 Boxster

00 C230K Sedan (sold)
87 420SEL "Phatryd" (sold)