ayahuasca, man you've really done some research lol. I actually had a friend who tried it but it didnt do much for him and didnt help his stuttering. I dont recommend any of the other drugs you listed. The only method I know of to not let stuttering hold you back is to not let it hold you back. But thats 100x easier said than done. So we gotta ask what the issue is. I've found the more we try not to stutter, the harder the stuttering becomes. Tricks, techniques, novelties, they all focus on trying to mask the problem rather than resolving it. The only way I can say to truly get past it is you need to learn that stuttering is ok and give yourself permission to stutter. This will allow you to speak exactly the way you want to speak and say everything you want to say. If you live in america or can fly in, The NSA conference is the best resource available for people who stutter. nothing else compares. www.westutter.org. I cant recommend it highly enough. During the off time, this podcast is really good and has given me a lot: www.stuttertalk.com