Alfa used the slotted grill on the 145 and the solid one on the 146.
I do not know if it will really make a big difference but if you can lay your hands on a 145 unit put it on and see what happens.
There’s a big difference between removing it completely and using a unit that was made by the manufactures.
If you remove it completely it could result in a lot of turbulent air damming in front of the hole which will result in bad air flow.
But with the 145 unit I assume that it was designed to allow additional air in since I personally think it is ugly compared to the 146 unit so Alfa used it for a reason. And in my opinion aesthetics wasn’t the reason.
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