What about trying one of the Natural Balance Limited Ingredient Diets, such as Venison and Sweet Potato, to see if that helps? At least pumpkin and rice is better than the intestinal stuff my vet always wanted me to feed for a few days. That crap had ethoxyquin in it!!!!!!
Or, you could homecook or go to raw, which is what we did. I like the raw because there is only one protein source in most formulas. Just don't assume the NV chicken is only chicken, it has turkey in it. We learned that the hard way
Good luck with the smooch-a-roonie! xoxoxox