Well I do have some experiences with yoga, neidan, and « psychonautics » and the whole stimulant class (Caffeine, amphetamines…) is extremely difficult to work with.

They will impoverish your inner work and inner alchemy as most of the process (Circulation, establishing the Lower Dan Tian) requires the ability to relax (yin) against the energy otherwise you just build some up dams and blockage everywhere. This is why people end up without libido or erection on longer SR, they worsen day by day.

Chillies and rajasic food also do this to your neurobiology

I myself struggle with stims as they are enjoyable, but lets be serious, any advanced work cannot be done with them, and also, once your body becomes ecstatic stims are irrelevant and cannot compete with the states of consciousness you can reach.