If you are going to plug the hot air inlet in some way, make sure you have the flapper valve securely fixed in the cold air position, or removed entirely. Otherwise it blocks the cold air inlet off...so you have no air.

There's no point in enlarging airbox holes or making more of them. You have a ~100HP engine there, and the stock inlet and filter is more than big enough to feed that. Look at your inlet snorkel in behind the grille - its opening actually faces away from the airflow. This is to prevent force feeding of bugs, rain, snow, dirt particles, etc, into the inlet system. Stick with the way Volvo made it.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)