part number 5213850010
FRONT BUMPER ARM MOUNTING BRACKET NO.4

52138C is the part in the image. =P

 

looks like one of the clips that bolts the undertray to the bumper, though hard to tell.

EDIT: more likely a bracket that supports the bumper there.

 

I actually bought that part since I was trying to pick up all the parts that hold the front bumper. I have not put the bumper back on yet so I can't say what it does but it seems to attach the bumper to something else. I have the same kit as you so I'll see whenever I get around to it. Are you having any issues with yours?

 

I was browsing and thats the only things missing from my bumper. I have new oem brackets that mount in the corners waiting to install. Seems like my aero was just slapped on and I plan on remounting everything when I get it painted this year.

 

When I had a repaint about 5 years ago I got my LSportline put on and did not pay attention to the fitment. The shop seemed to just slap Mines on too. Now that I've been doing a slight rebuild I notice it's not flush especially the rear bumper. It seems to be sagging a little like they did not tighten or align it properly. If you don't mind could you post some pics of your rear fitment in this thread or PM? When I took the front bumper off I see they didn't replace the mounting brackets that connect to the bottom of the fender. I'm trying to get everything lined up properly for a respray.