I had the most annoying squeaking coming from drivers side front somewhere, it got to the point where I was considering trading in the 4runner for a newer one then I came across this post:
https://www.toyota-4runner.org/2825358-post23.html
Turns out that was exactly what mine was, the little plastic piece rattled so much it took the paint off the metal behind it. I used double sided tape, and better clips and it went away.