Yeah Power Drive is hit or miss..
When I notice it works 'better' is during hard cutting a long time AFTER a carbup or cheat meal. The Tyrosine converts to Epinepherine/Norepinepherine and Dopamine. I won't go into detail here with conversions etc, but the feel good effect is from there.
So Basically I'd Pulse fast a day before a high carb up and I'd notice a nice little effect during the day. Since it was so long that I'd been depleted the Dopamine, and adrenalin converted from the Tyrosine was really noticeable.
Other than the pulse fast, I've only ever used one serving pre or post workout. I'd like to take 2-3 scoops post workout purposely over-training to really gauge it's effects for a week.