These pieces are pretty important pieces to the cooling of your car. The lower piece creates an area of high pressure in front of the radiator and slightly lower pressure behind it. The upper piece keeps the high pressure from escaping over the radiator and instead it goes through it. Thus, you get more air through the radiator than if they weren't there.

The radiator doesn't see much air otherwise due to the front design on these cars.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas