I have been having issues with my bumper since i bought the car, previous owner hit a curb snd broke the bolted brackets, so the corner has been hanging. Also, it sagged underneath and caused scrapping and flapping. Also, due to the gap, wind got in there and pushed my wheel liner into my wheel and melted a hoe in it. Zip ties never really worked.
So me and my bud removed the bumper and splitter entirely, brought it into my apartment where i cleaned it, dr colorchiped it, and bolted that b!tch together once and for all. I installed new pop rivets in the wheel well/splitter overlap, they were missing on both sides. I also put in 3 new pop rivets underneath which pop into the allyminum frame, that fixed the sagging, wasnt particularly obvious that they were missing. Not sure if they fell out, or a dealer did an oil change and never replaced.
Now its all rock solid, no/minimal gap, no flapping bs. Because the bumper was not attached to the sitter for so long, it became slight distorted, so when i bolted it to the splitter, and went to attach both to the car it didnt want to line up, we had to install it like 5 times attaching parts in diff order to get it to work.
Then i washed it.