I first went to the Car Talk web site and there were two instances of something like this happening to others.
Another possibility here. Have you removed the air cleaner top and verified that the air cleaner is not full of stuff stashed in there by rats?And I also found this on a Prius chat site.
Slim odds I know but a VW was towed into the shop one time that would barely even run and the housing was completely full of dog food. Rats had gnawed their way in and had turned the air cleaner into their own personal bank vault. The owner stated that he had noticed the car running worse and worse over time.
I hope my mechanic can cover up some of the inlets with screening as suggested in the articles. I’ve heard of rodents chewing on wire but never stashing food in a car. Ugh.