Go to this thread and look at the attachment of the first post...this is the rust I am referring to. I just now found this way after posting mine...lol.

https://montecarloforum.com/forum/sh...ad.php?t=23687

 

Thats from dirt getting in between the bumper cover and the quarter panel. Thats actually not a bad fix if you have some sheetmetal tools and a welder. I not to long ago repaired a lumina with rust like that on both sides. I cut the rust out, made a patch panel and welded it in. The best part is you can get behind it and primer/rustproof it when you are all done, so the repair will actually last.