Yep, you'll want some sort of lower ground effects to push the air around the car instead of under it. It looks like SE-R bumpers have a similar stagnation point so perhaps look at "tuner" (aka rice) bumpers or other front splitters on Ebay. This one looks terrible but at least has that lip that will keep air from underneath the car.
Color match it and no one will know.
You could easily block off those useless grille openings on the sides and it will look nearly stock. When blocking the bottom grille start from the outside and move inward; this will encourage clean flow to stay clean as it goes around the car.