After hitting few stop bumps the center narrow vertical piece in the bumper, holding intake air foils parallel, cracks, causing the lower air foil to start drooping down (no longer parallel to ground).   To fix that, I have cut out of thin aluminum sheets, four pieces (I had two vertical pieces cracked) in shape of the bumper vertical section that cracked.  I have drilled holes through the aluminum pieces, marked up cracked area on the bumper and drilled corresponding holes.  The, have used epoxy and rivers to hold it all together.    Years later - the bumper air intake vanes are perfectly parallel to each other.