From my knowledge it is just the extracted compounds used. Yes Powerfull does cause me to become lethargic, and that was the nature of the original extract. The new one I believe does not cause this as badly. The original helps me wind down at night and get some great sleep which is why I still use it. I think the extract used in the original was Muira Puama.
Now if you want similar (in my oppinion better results) when it comes to libido and strength and explosiveness in the gym without the lethargy side effect go with IGF2. Its great and has multiple extracts that will aid in testosterone.
I am by no means an expert but I would say you should use IGF2 post 4ad cycle. But I will let the real expert RMS handle that.