If you are getting this heat thing then it seems like there are plenty of alkaloids in it. Certainly some Yohimbe I've used has been pretty crap.
Yohimbe unlike Ephedrine (a beta agonist) is a selective competitive alpha2-adrenergic receptor antagonist.
I used the Twinlab variety for quite a while back and got some good results from it also before Viagra was out stuff like Yobine was sometimes used to treat erectile dysfuntion. Its a vasodilator basically among other things.
DON'T take it with the ECA or Ephedra on its own, I know you have used Eph from your other posts, and DON'T take it with anything like HOT-ROX. Also don't take it with much caffeine and not with anything containing theobromine, like hot chocolate.
Also, avoid tyramine rich foods like cheese and wine and cold medications and stuff containing phenylpropanolamine which are usually allergy medications, cough and cold medications and some other similar things.
Taking it with other stuff as mentioned above can cause high blood pressure and other pretty bad side effects like extreme anxiety.
I took it was Sida Cordifolia (basically a plant containing ephedrine and pseudoephedrine alkaloids) and I was FUCKING ill. So be careful.