The whining noise on startup is your air pump, part of the emissions system. It cycles on more frequently in cooler weather.

The symptoms you describe on decelerating sound like a timing problem, don't they? You don't mention how many miles on your car, but if it's 70k or over, I'd urge you to get the car to a dealer or qualified indy tech and get the timing belt changed. It's possible, I suppose, the transmission could be cranky...an oft-cited issue on this board. I, too, occasionally feel a hiccup which seems to be associated with the transmission. One of the most frequent admonitions on this board is to *completely flush* and refill the transmission with fresh synthetic periodically.

Mrsha's suggestion to check all turbo air lines is very good advice. Inspect for softness and cracking. Typically, if there's a problem with the turbo, you feel the problems on acceleration. You probably wouldn't get to 85mph with a compromised turbocharging system.

The turbos in this generation Volvo are quite reliable. I suspect your problem is elsewhere. Good luck. Let us know how this turns out.
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)