is the material on the black bumper for the Willys different than the sport s? Do you take care if it the same way - same protectants to keep the black color?
same plastic, 303 Protectant or Adams VRT, or both
Use a textured sponge to appy, you can get them cheap from Crapazon
303 doesnt air dry and stays as an active protectant, if it gets wet it will run and needs to be smoothed