While having the greenwhisker buff (increase pistol shot damage by 300%), using pistol shot does not use the buff. Pistol shot does normal damage, and the buff remains on you. The next pistol shot will use the buff, this is a waste of energy as you have to pistol shot twice just to use it. I did not notice this happening until I got the 2 set, so the 2 set may possibly be the cause.
Edit: Unequipping 2 set fixes it. So, while having the 2 set bonus pistol shot may not use your Greenwhisker buff. Great.