Strange, Fenben is now very stimulating to me?

After years of herxing and fatigue from sporadic fenben use, I am now getting a stimulating effect, its like stronger than coffee kind of energy.
I am confused. I like it, but I am confused, if all the stuff is cleared out finally, I would think it would just have a neutral flat response. I am not sure what to make of this. Maybe it is doing something to the mitochondria. A similar thing happens to me from metformin.