No idea why it causes acne in susceptible individuals, but I assure you this does not happen to everybody (in my experience, it doesn't even happen to a significant majority of people).
Maybe it could be through the transient insulin-resistant state that it puts you in, since I know many people are susceptible to insulin spikes and acne, but that is just conjecture on my part.
I would just go with Ephedrine. That is the compound that works for fat burning and does aid in appetite suppression. I do not know the other compounds in Ephedra and IMO if they are not needed I wouldn't use them.