carbs
Start by cutting them ALL out for a few days, until you're pretty much gas free. Then add back in ONE specific carb for a few days and see what happens. If everything's okay, then add another specific carb. Repeat as necessary. And remember that lactose---milk sugar---is often the culprit for many people.
I cut out all gluten and dairy and have not had ANY gas/bloatey feelings. I eat complex carbs that are slow digesting. Sweet potatoes, quinoa, steel cut oats. I eat these every day. I might splurge on the weekends and eat a gluten free english muffin with natural peanut butter. Since cutting out the gluten my body just feels SO amazing! OOO AND I started drinking psyllium husk in the morning and that also helps I think taking away the bloat. GOOD LUCK!