I would get a barn cat or something to help deter the mice from making the truck a party habitat for them. If the mice are into your hood liner, next up is wiring. Also one of the ulterior uses of a hood liner, is in the event of a fire they are designed to fall onto the engine and assist with suffocating the fire. It doesn't always work, but that is one of the theories beyond noise dampening and under hood beauty. Just keep in mind, if you remove one source of enjoyment for rodents, they will find another