wen i shut my car off you can hear this sound from the gas cap area wen you turn the gas cap it sound like air is rushing in can any 1 tell me whats wroung?

 

Nothing.

It's actually pressure. It's supposed to do that. In fact, in alot of places with emisions inspection, one of the things they check for, is that your gas cap holds pressure; your car will fail if it doesn't.

If your car makes a noise like a goose honking or something, maybe a couple or 3 times over a period of several minutes after you shut your car off, and it seems to be coming from the rear of the car, it's the little plastic vent valve in the rear end tunnel just inboard of and to the front of the left rear tire.