Richard,
I have the same issues with my 2002 S60 2.4t. The revs pick up then drop, pick up then drop....... It does it when I'm slowing down, stopped or idling.
I'm assuming this is the same issue. I've only just had my car serviced and i've just noticed the problem since the service.
Not sure what can be done about it, other than request a new one be fitted by the dealership!
Best regards
Steve
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