On the 2004 Cooper S, I had to replace the bumper cover and the old grill was held in place with 4 metal tabs. They were jambed in to afix the grill to the old bumper cover.
With the new bumper cover I don't see where the old metal tabs would go. I put the old grill on and it just snapped in without metal tabs, so I am wondering if I should I just discard the old metal tabs.