I used to have a cat with sinus problems (allergies!), and she would snore and wheeze when she slept. Most of my cats now don't, but every once in a while, Scooter (the oldest) will "whistle" or wheeze in his sleep. He also twitches his whiskers. I used to have a cat who would make little meowing, chirping sounds in his sleep. Must have been dreaming about chasing a mousie!