IBD is diagnosed definitively with biopsy, is my understanding. I went thru a number of prior procedures and tests before doing that. However, many cats are managed just by changing diet to a 'novel' protein that they haven't eaten before. THese are prescription foods or you have to make them yourself (I tried that for a bit, but the cats didn't like it any better than the canned stuff), like IVD (a brand).

Which is not to say it's necessarily IBD, but throwing up that much probably isn't 'normal.'