Thank you for your ideas about the tahini dressing and leaving yogurt out for 10 hours.
Just wanted to caution that some people are allergic to onion-garlic, and to green/virgin olive oil (me included). Read all the onion allergies on About.com
In powder form (or well-sauteed with water added) onion-garlic may be less problematic.
Also some people (me included) are allergic to [fresh] pineapple, kiwi & citrus.
Also, re: Stevia, I'd read an article by Bev Laumann (of ic-network) who said she tried both Stevia & Splenda, and she found Splenda to cause her a bit less of a reaction than Stevia. And since she's very sensitive, she may be like the miner's canary (i.e. the "acid test")