Greatly amplified by weed or not really in your opinion? I would say so personally, but it seems that opium has a very subtle effect overall.
most definitely amplified by herb, personally, id throw a benzo in the mix as well (xanax, valium, klonopin)
Well, in my experience, it hits almost instantly. It can creep up on you if you're not careful too, so don't smoke too much.