Edgun Leshiy 2 Power jets are used to control the valve dwell time.  Dwell time just simply how long the valve stays open.  The longer the valve is open the more air can pass through the transfer port.  the speed of the pellet is determined by both the pressure and volume of air pushed through the transfer port into the barrel.  Think of this as Volts (pressure) and ampere (volume).  Together these will determine how much power the gun is set at.  Think of these jets as your hammer spring tensioner 

Before opening the gun and changing jets make sure you have a CLEAN environment free of dirt, debris, or other potential contaminants.  It is important that the valve itself never gets dirt or debris introduced into the mechanism