I've found with my clients that cat foods with grains can cause some minor bloating and gas because it sits in the digestive tract longer and expands releasing air. This is usually solved by moving to a grain free preferably canned or raw diet, sometimes the grain free kibble can work but that depends on the cat.
Also probiotics will help the digestive tract and can help gas and other digestive issues. Just make sure it's 1 billion micro organisms or more, that's human grade anything less isn't really worth using since it wouldn't be potent enough.