Well, we are extremely new to biomed but we've had some really good success so far. I haven't tried much but here goes:
1) Intunive: A medication, I'm sorry but he went from horribly explosive and attacking people to sweet and calm with few tantrums.
2) DMG: Instant speech where before he had none. He literally began to use some single words within about 24 hours and has begun some 2 word phrases. Made him very hyper, though.
3) Folic Acid: Added this to calm down the hyper from DMG and his speech got more clear. I realized he's been saying a lot "mumbling" but it wasn't clear enough to understand until now.
4) Sugar-free diet: More calm and focused, much less defiance
4) Daily speech with me at home using flash cards and labeling (he knows about 200 cards now and says half clearly with the other half close approximations).
6) Solaray yeast cleanse: A few days ago. Wow, now I know what yeast is! Yuck.
7) (Can I have seven?) Omega 3 Fish Oil/Melatonin: Allowed him to come off 4 years of Seroquel to sleep at night. He hadn't slept unmedicated in that long and he literally fought it even then until he was "knocked out".

What about an 8? GABA. Just started but already less vocal stims and trying to stand on his head. We're still trying to figure out dosing and timing but it definitely works for him in a good way and great with the DMG at the same time to balance out the hyper!
What didn't work:
1) Ginkgo Biloba: Made him crazy and wild, he could not sit still and recently acquired language was gone on the days he took this. I finally researched the GABA/Glutamate stuff. I'm learning!
2) Nasal B-12: Had a short run with this and it did nothing. He wasn't an instant responder like some.
3) Oral B-12: Same as above. In fact, both seemed to make the DMG less effective for speech oddly.
4) Enhansa: Nothing either way. No yellow poo, no yeast die off, no nothing. We got up to 600 mg with still nothing and decided to try Solaray. We had nasty yellow poo the next morning that smelled disgusting!
5) Years and years of the doctors treating him with medications (Risperdal, Adderall, Concerta, Focalin, Methyline, Clonidine, Seroquel, Valium)! They only made him worse and more withdrawn.
6) Peptizide and Culturelle: At least it didn't eliminate any yeast. Nothing happened. We thought he didn't have any until we added the Solaray recently.