nope it's worst now, If possible can you send me the file before this modification. If you use blender you can reopen .blend1 .blend2 Explanation of what was going on : When you added those faces on the bumper, bender didn't know how to connect it to the previous uvmap so it's create random weird value. That's why there is weird texture on the new thing. When you edit the uvmap of an official vehicle you should keep in mind that the uvmap should be as close as possible to the existing one because skin and texture will not work.
How can I do that myself? I have multiple other mods that need a shading fix and I can't have them all fixed by somebody else for me.
to fix your bumper the only thing I did is to move the UV points that where gone wrong. You can use the texture of the car to help you Select only parts that need rectification and a few border faces without modification to allow you to put back everything easily. Don't forget that you need to do this to 2 uvmap map-0 is the car texture map-1 is the skin texture
I noticed that the shading was still a bit broken: So I decided to fix that myself. Am I doing it right?
You are mapping your faces wrongly. You basically have to match your UV to the original texture of that vehicle, so that the part you are mapping matches one of the body-parts and so on.
