1996 Other Mitsubishi Models Sucking air

Overnight my car, at idle, sounds as tho it's "sucking air." (Sounds like in the "old days" when you would take the air cleaner off vs having it on). I recently was caught in flood water and am worried I have done some type of damage. It doesn't appear to hinder the way it runs or performs, just has NEVER sounded like this before. My "check engine" light has not come on, but this has been a wonderful car.I serviced it as recommended and I would love to put another 75000 miles on it. Any suggestions as to what I should check first? Please, any help you can give will be appreciated.