When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Steps 1-18 of that pdf document reveal how to remove the top grille of the 4GS.
I didn't remove the bumper but the chrome trim around the top grille is actually screwed into the bumper (the mesh/slat plastic grille is clipped into the chrome trim). When i had all other bolts/tabs/clips removed, I yanked the chrome trim/grille forward and "broke" it off the bumper frame. Those screws i mentioned are on the bottom-most part of the chrome trim where it angles down and sits on the front bumper on both sides. Very difficult to get to without removing the entire bumper.
Do i have to take off the bumper to take off the top grill?
If you can find a way to get to those screws behind the end-tips of the chrome trim (as shown below), you won't need to remove the bumper cover. I didn't see much room to get to them when I had everything else open as the bumper foam/real bumper was in the way but i'm sure if you're inclined, you'll find a way that your most comfortable with!