Be careful woth kambo if you have an heroin addiction. My kambo practicionner explains it better than me, but you have to be very careful about opiates when using kambo, or it can kill you.
I have no experience with iboga, but for an opiate addiction, from what I have read, it would be my first choice. An opiate detox in a safe setting with someone who knows what he is doing with iboga.
Kambo works well for other addictions, but if you're regularly on more than a very small dose of opiates, kambo is dangerous.