Outside cold air mysteriously getting into car

HELP!!! I have a 1993 Volvo 240 wagon in great condition as my winter car. My problem is- I have COLD outside air mysteriously entering the interior of my car (and that outside air is MIGHTY COLD in Buffalo during the winter!!). I feel it coming out of my steering column, and most of the gaps in my dashboard & control panel area’s. The other odd part about this is that the airflow is intermittent- there is no pattern to when it happens or stops. I have had the firewall
seals/grommets, etc, checked, and have had the vent system also checked by competent car people that are very familiar w/the 240 series. No one seems
to be able to figure it out. Other than sealing up all gaps with rope caulk or tape, I dont know what to do about it…ANY SUGGESTIONS/ANSWERS???