[Formerly Steve Wilkinson]

You're gonna have to plug a lot more than the exhaust pipes if you have a rodent problem. It's probably more important to make sure the heater flappers are fully closed and maybe even taped over. Once field mice get in there, they make a huge mess.

I've also had mice climb up inside the B pillars to the space between headliner and roof and make nests up there, and I have no idea how to prevent that.

Basically, if you have a rodent problem, it needs to be solved before you store the car. There's nothing on god's green earth that will keep determined field mice out of a 911--not magic potions, not fox pee, not mothballs, not dryer sheets, not even a shaman dancing around the car. The only solution I finally found, storing the car in a rural barn, was a serious, zippered, heavy-gauge car bag.