I recently swapped knock sensors on a Camry V6. When I pulled the intake, the area between the block and the intake was filled with fuzz, and nesting material.
There was also a bunch of mouse poison. If was a friends car, and he had recently noticed mice in the garage, so he put some poison containers down. Apparently the mice liked to transport it to the engine, lol.
I also have an S10 that was running real sluggish. So I checked the air cleaner, and it was packed with nuts and fuzz. I also pulled the intake tube, the fuzz was so packed in there I had to use a long rod to shove it out. It was like I picked up twice the power when I got that out, haha. Mice!!!