There is a thing called a windjammer that mounts to the windshield header when the roof is out. It cuts down the cabin turbulence. The thing pictured almost looks like a wind jammer stuck into the rear header. Never seen one , can't imagine it does anything.
No Murray, please, anything but a minivan! I've been nursing my C4 for 20 years and it still puts a smile on my face. If I want reliability and easy access I drive the Honda Accord, but never get the smile.