Passing wind in cats or kittens often results from a poor quality diet, and is mostly related to cheap wet canned food which is sometimes mostly water and fats. Since you are feeding your kitten only dry food it is unlikely this is a purely dietary concern. You should have your vet analyze a stool sample from your cat. Your vet will probably look for potential imbalances in the stomach acids/enzymes and also for the possibility of a worm infection, of which flatulence is often a symptom (though not usually the only one).