Now we want to start cooking for him, as you already said better to start with 1 protein type and i read that it is good to try gradually changing to new protein sources, to see which one works for him. We will start with chicken and then in a while if it won't work try turkey. Of course change in diet is on its own a reason for diarrhea so i am not certain how gradual should we do it not to bother his stomach even more. We kept on changing his diet lately too often. If i recall correctly you mentioned earlier that you are feeding homemade food as well, How did you introduce it to your cats? We know for a fact that Chico will love it, there are no worries there. We are still considering to try Thrive for a while, but since it is much more expensive, we probably won't be able to do it for too long and introducing a new temporary food won't help his GI. Of course there is always in the back of my head the constant question: what if Thrive would help? And to be honest if it did i would rather save on electricity in the house than on stopping his diarrhea...
Are you doing a homemade raw diet or a homemade cooked diet?
Thrive is expensive, it's not the only food George get's he just gets one tin a day. Once you have Chico figured out it might be an option as an occasional meal. (George only get's thrive for breakfast), I have all my cats on a rotation of a number of different flavours and brands, but not homemade, I am considering it for one of my cats who is CKD and has heart trouble.
On Wednesday we will have to go to the vet again for an Ultrasound and i am afraid that the next and only thing other thing she will propose will be a biopsy. I would hate to have to do an invasive procedure to Chico

Have you ever have to do any invasive procedures to George?
The only procedure George has had was removal of all but his canine teeth, his mouth was in a bad way and making him very ill. But nothing other than that.
The IBD website
@Wendy&Neko linked for you is a very good resource for IBD. A number of our IBD and FD kitties use that site for info and advice (well their CG do

)
Wendy was telling me that she transitioned her Neko from canned to a homemade raw in two days, so it just depends on if the kitty would go for it.
I'm glad she posted about her experience with IBD both with her Neko (who also had FD) and with her non FD kitty.
Was considering it as well, thanks for the idea.
We are extremely erratic in the foods we are giving him, i know

but we keep on second guessing our decisions. Now we are going back to the hypoalergenic kattovit (we are doing it in more gradually), because Cosma contains Cassia gum which is in itself a possible cause for IBD... So today we transition to kattovit and tomorrow we will gradually start introducing the homemade (if i will be successful in preparing it)


Poor little Chico for having to go thru all our indecisions
I'm sure you will get there, with FD there is a lot of new things to learn, and having to deal with the possibility of IBD/food intolerance and figure that out as well must be overwhelming.
You asked about the 6.5% affecting his BG/insulin needs over the last few days when that has been the only food he has been given, in theory it shouldn't make a huge difference to his BG, but that can depend on the cat, some are more carb sensitive than others. After last nights cycle, where you fed 2% for his snacks instead of 6.5% his BG came down. Something to watch, it may just be a coincidence.