If the center (center arrow) part of the body work directly below the two louvers on both sides of the car are hanging lower than the sides OR that same area is "sucked up", you've got the dreaded "Bumper Sag". The panels should be straight accross, parallel with the louver openings.
IMA, I have seen new Vettes on the car carriers being delivered that have the problem, I know of a few dealers that blamed it on aftermarket exhaust and customers went to the parking lot and showed the dealer new Vettes with the problem.
I had to install one on the passenger side of my car. Never noticed it until I got to Zanioing the rear end. The rear fasica braces do work, but put some two sided tape or silicone caulk on the side that contacts the fasicsa to hold it in place more securely.