Actually, being that Chongo is from the same breeder and I'm sure a part of the lineage is the same, he does have a very sensitive stomach. Food changes are very tough, and straight up Royal Canin Kitten 36 Kibble or Evo Turkey and Chicken kitten formula (not real fond of it) will give him loose stools and often severely gassy, clear the room bombs. I could not get any canned food in him early on as it was just running right through him, be it the food that was provided to me (Evo Turkey and Chicken Kitten Formula) or any of the other high quality foods the local pet stores had. That's when I went with a raw diet for him as was sent along with him as when he first came home, and from there I have been able to tinker with what I can feed him.
Anyway, here is a set of brief notes.
• He does not like turkey in any form, I'm talking hunger strike levels of dislike.
• If more than a third of his food is the Evo or Royal Canin kibble, loose stools, count on it.
• Raw food, he doesn't tolerate a lot of egg in it and also doesn't like fish oil.
• Cooked salmon to provide the same quantity of fish oil as the capsules, loves it.
• Gizzards, no way, he can discern if you even waved one above his food.
• Loves the reduced protein food given to our eldest cat where about 20% of the protein has been replaced with butter and pumpkin.
• Wild Trax supplement, hates it and it needs to be disguised well and at about half the recommended rate, never sprinkled on food.
Prefers cooked poultry over raw and I've taken to a quick jaunt in the oven before grinding chicken thighs (less than 10 minutes).
• Duck, definitely loves it and I mix it with some pureed peas (about 5-10%). Looks gross, and it's more of a treat than a staple food.
That's about all I can think of off the top of my head and the comments about reducing some protein rang a bell as Chongo will always make a dive for his big buddies chow. Wanting to make sure he gets the protein he needs, I dissuade him from eating it, but he definitely likes it.
Lastly my ventures into raw came of necessity as opposed to any want of grinding up raw chicken and the like. He was doing fine on the Raw Holly and Dale provided me, although as soon as I was out that's where the loose stools started to occur. I scrambled, trying to get him to eat anything that he wouldn't have digestive issues with and not until I got back to raw as a basis could I successfully transition him to anything else. I'd also compare some notes with Rascal as he's got a few from Holly and Dale.
Hope that helps!