LOL. It is supposed to get warm enough to light up my snowflake this week! It has been a little nippy.
The recirc switch should NOT be in the closed mode, except for cooling the cabin off in the summer, and then only for a minute or two. Fresh air needs to enter the car from the front to keep air entering from the rear exhaust vents.
If the outside air is too cold, close the center dash "fresh air" vent. Leave the system on auto, or turn the fan speed up to get more hot air flowing through the system. But do not turn off the recirc switch.

Air will come in through the door seals if the outside vents are shut, so that air will enter through the door handles and window switches. The faster you drive, the more air will be drawn through, and the only counter balance to this "problem" is to turn up the heater fan with the recirc off.

The noise you hear is normal with the recirc sw on. There is a little air getting around the flapper/damper due to the high amount of negative pressure in the cabin.

So, for winter time heat rules: Close the center outside vent in the dash. Leave recirc/AC switches showing green lights. And when the fan speed drops because the cabin has warmed up, slide the speed switch to the right to force more heated air into the cabin.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)