For me in my A4 chassis, the favorite place for rodents is behind the cabin air filter if not directly on top of it. They make the nest there, using fibers chewed out of the hood liner or even the battery blanket. I have eliminated both, and did that up in NH in spite of the cold.
My solution is to use green mouse party food sold at hardware stores for killing the rodents. Half a block behind the cabin air filter, and the other half in the bottom of the engine air cleaner box. I have had them in there chewing fibers from the snow filter that is glued to the underside of the air filter, and using that for nesting material as well.
That mouse party food is great. They party, eat up, do weird dances the next day, then never dance again. And they don't chew up the wires because, like above, they aren't there long enough.
Cheers,
PH