Overheating at idle

I ran the car this evening and found a ton of HOT air is just spewing from under the car. I suspect that a lot of this hot air is cycling back through the rad. I was going through some parts and noticed I haven't installed the splash guards yet. Not sure if thats going to be a game changer with airflow? I took some pics and in the green highlighted areas, would adding some panels to cover those areas be beneficial? I'm thinking maybe than hot air won't be short cycling back through the rad and seems like a lot of the newer vehicles have plastic that is covering this area.

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I've preached that a lot on here before and it falls on deaf ears. You look at every new car made and the under side of the engine bay is closed off so that air has to be forced through the grille and radiator.