does the plastic air director/ under radiator cover actually serve much of a purpose? does it actually help direct air thru the radiator? Ive had it off the car since i bought it 2 years ago.

 

Well it's been off for two years ... if it doesn't overheat don't worry about it.
I have one hanging over my workbench as my wife can't remember to stop before she hits the parking stop and she's brought it home a couple times with only one or two of the plastic rivets holding it on. It's a lowered Thunderbird SuperCoupe.
But yes the engineers do put those little dams and spoilers there for a reason and it is to modify air flow.