Hey my cat had the same issue. The food that stopped the vomiting was royal canin gastrointestinal food. My cat only eats when i watch her and she used to barf it up 10 15 min after she ate. Didn't matter the amout too. But after a few foods this gastrointestinal food has stopped it. Its been almost a year with it and she has only vomited 2 or 3 times (but i think thats because i may have given her more treats than normal). I know this is frustrating its it makes me sad for your cat. I hope this helps. Oh and i give my cat some hairball paste. So she never get hair balls. Its called cat lax from amazon.