Hi Ukhen,
(nice moniker...very cute)
Well you hit the nail on the head, you need a food diary detailing not just what you eat but what you eat with it (drinks, liquids, drugs...), the times of day that you eat and your general heath at the time (an Exel file should make it easy to do an much faster to compile the data).
That will give you a general idea of what your pouch likes and doesn't like.
Next you can retro-engineer it and try an eli;;nation diet...Start off on the 1st day with something easy like fish or chicken...then each day add one food to your diet and see how they react both alone and together.
I have a general rule of thumb...most of us tend to be lactose intollerant (not all but most colonless people are...but many can still eat ice cream , hard cheeses and yoghurt), next high fiber foods can cause some of us problems...things like mushrooms, beans, corn, leeks, certain salads etc can be problamatic. (again, many or us learn to chew, chew, chew and manage to navigate the pitfalls of fiber).
Some of us cannot tollerate carbonated drinks or beer etc (sorry)...so they tend to avoid them. Others feel the same way about fruit.
Again, a lucky few can eat anything and everything not nailed down (argh!) while others seem to live off of peanut butter and jelly sandwiches for the rest of their days.
Act as if your pouch is a 3rd twin (by the way, congratulations!)...Treat it like a baby leaning to eat, purrée your veggies, avoid chunks, test foods for a few days before integrating them into your diet...be nice.
by the way, just because a food disagrees with your pouch today doesn't mean that it won't work out later in life.
Good luck
Sharon