As far as I know, NPA has a similar amount of androstenone in it as Primal Instinct. Did you dilute NPA?
Are you sure? I think Primal Instinct is more per drop. But I actually think it may also be because Primal Instinct feels more animalistic/aggressive as it’s more purely androstenone, while NPA feels more sexual/smooth, and it’s rumored to have an additional secret ingredient.
In this chart from LS it shows Primal Instinct to have a tiny bit more pheromone content per milliliter: http://pherolibrary.com/reference/product-table.html
I don’t know though, there were lots of discussions on LS about which one is more androstenone, but for me at least PI feels like a real kick, while NPA is more user friendly 
…and I also think that typically I would wear dabs of NPA, versus using drops with PI. Dabs are less than drops, so perhaps that also plays a role in it. But overall, I think PI acts differently than NPA. PI is a bit more on the aggressive side. NPA is more sexual, but it doesn’t get too out of control for me.
But to get back to the topic of the thread, I have to say, NPA also has a similar affect of “duping” except that if I work in some nice conversation, the combination of the NPA and the conversation really make a solid impression on women. I think what it comes down to is that the stronger the androstenone you’re wearing, the more you have to “bring it” in terms of acting the part.