wegweiser

Center of the hood, engages/buffers the hood latch, toward the windshield when hood is closed. 

That type of clamp is referred to as an oetiker clamp, and the tool required to properly cinch them is a little unique. The "good" version of the oetiker pliers have a cam that squashes the hoop down, as the jaws cinch the clamp. Takes practice to get 'em just right. 
 
Here's a rather affordable version of the tool...no idea if it's as good as the expensive ones....but the expensive ones are sweet and work great.
 
http://www.autozone.com/test-scan-and-specialty-tools/cv-joint-boot-tool/oem-cv-joint-boot-pliers/141501_0_0/
 
Is this an original BMW / Bilstein clamp? No idea. They're found all over later BMWs though.