My cat is vomiting

What did the endoscopic biopsies show? If everything else has been ruled out then you need to be concerned about a food intolerance and/or a motility disorder. My therapeutic plan would be as follows: No food at all for twenty-four hours. If there have been no gastrointestinal signs by the end of the fast, then you can reintroduce very small portions of a bland, high quality food such as Stage 1 baby food or a home-cooked wet rice mixture (regular rice cooked with twice the amount of water for double the amount of time until it is a "mushy" consistency; mix three parts of this with one part boiled white meat turkey or pork). Give him only one tablespoon at a time, several times throughout the day. The fast followed by the small frequent feedings will allow the cells lining his gastrointestinal tract to heal themselves. You can then gradually increase the quantities given at each meal up to 1/4 cup twice a day. At this point, if he is still doing well, then you should consult a trained vet homeopath for further care.