Well, I'm now pretty sure it's the agave. I usually eat it in the morning with tons of food (3/4 of my food for the day is usually eaten in the morning) and just have diarrhea, but no gas or pains or bloating or any of that other nastiness. But yesterday I drank it in my iced green tea in the afternoon without food (made it in the a.m. but never got around to drinking it.) My tummy got rumbly, but not too bad. But in the evening and last night? Egads! Massive gas...at one point I woke up from a stink, thinking the dumb dog must have had an accident, and realized it was me! Then diarrhea off and on after that.
In general, Plucky, sugar in any form should be strictly limited for type O's. If I use agave, it is only in a recipe that calls for sugar and I use it probably once every two months or so. We get enough sugar from fruit. I limit my fruit as well to about 2 - 3 pieces of fruit per week.