Designed for cars participating in the WRC during the 90s these scoops were designed to pressurise the cabin to help keep dust out on those twisty gravel stages and allow fresh air in the non air conditioned cars. Note that Air Condition adds weight, robs power, and is something additional that may break, and also you really can't roll down windows in a rally.
This mode is not cheap and not for the faint-hearted as it requires you to gather the balls to cut through the roof of your pride and joy which is an irreversible mod. The reason the parts needed are expensive because the Spec C models were rare to begin with, so not a lot of used vents come up for sale. Currently used roof vents start from around £300/$400 roof vent, and go up in price from there depending on the condition of the plastics and rarity - £400/$500 roof vent and £450/$600 roof vent. There are also new ones still available at £700/$900 - Genuine Impreza Blue Spec C Roof Vent.
Note: This modification was made to a 2001/2002 Bug Eye Impreza Subaru Impreza sedan, other models installations may differ slightly.
Photos by Michael Xavier