Hi Alinus,
Oh the old inulin FOS / Inulin issue eh? Actually I forgot to mention that, so thanks for the reminder. Yes, inulin used to bring on AS in me, although no overt digestive issues otherwise.
I was able to build tolerance to it by starting with a tiny tiny bit of garlic swallowed whole with water, and then increasing the amount a little each day. Didn't take too long. Of course each persons gut flora / immune reaction is a little different but may be worth a try for you (if you haven't already). Once I was able to eat garlic and onion it did make cooking quite a bit easier for me.