Could be the SAI system, tends to run more in colder weather to reduce start-up emmissions.
My whine was fairly noticeable, but ceased immediately upon ejection of the ex-wife.
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Six speed 2000 Boxster S
Arctic Silver on Metropol Blue | LN Dual Row IMSR | Arctic Silver console, spoiler frame & bumperettes | Crios mod | Technobrace | RoboTop module & modified convertible top relay for one-touch roof operation