I'm not sure if causing you headaches is done through messing with brain chemistry in a similar way to highs or adrenaline rushes, but there have been some people that claimed to have reached some of these objectives.
Lessening pain: Many say that their tulpa is able to lessen or null weak pain a bit. However I'm positive that with a bit of practice one could reach the point to completely null even quite strong pain, but nobody I know of has tried that, since most people aren't constantly in pain, so there's no reason for them to try to learn that skill.
Also worth noting is that you can do it with self-hypnosis, too.
Adrenaline: Dunno, probably.
Highs: Oguigi said that she was able to give Koomer a dopamine rush
pony tulpa magic, they stopped soon after though since it was giving him strong headaches and because messing with brain chemistry can be dangerous,
dopamine has been linked to schizophrenia.Also worth noting is that a few months after
they did indeed develop schizophrenia, or at least something similar.But it probably wasn't
only because of that.
Also yes, I'll be willing to experiment as soon as able to, since I seem to be making some slight progress again.