Dave me and a friend are also trying to diagnose via tests what we have going on in our autistic digestive tracks and lately we are thinking that the G1 Effects of Metametrix that uses DNA testing should be the most accurate.
I feel like my intestinal problems are complicate enough to make worth investigating before treatig them. So far, NOW super enzymes or GB3 have ended with my constipation for good, proving by trial and error I had lack of digestive juices (either bile or the others).