Wheat and dairy seem to have no effect on me unless I have extreme amounts of them. Like a piece of bread is cool, but I've had weeks where like everything I ate was pasta, I get all bloaty with that.
This is gonna sound weird, but in Chinese medicine theory about ASD, Chinese medicine has food therapy. Where you eat certain foods based on yin or yang of foods, and how hot or cold they are in Chinese medicine terms. IE, egg plants are usually considered yin, and cold, whereas beef is yang and warming. So Chinese medicine says autists lack heat. Of course, in my case, I don't seem to, I seem almost the opposite. So you have to actually look at it all from an individual basis. But for most autists, a higher meat diet seems in order.
One thing I notice personally is, taurine supplementation helped me a good deal. There's supposedly a problem amongst autists where taurine can't be synthesized from other amino acids. Same with carnitine, too. So you either need foods with lots of carnitine or taurine in them (meat) or supplementation.