This can be a difficult problem to find even for a technician. You can check how the water is coming out of the valve first. Disconnect the power first and then remove the water line on the back side of the valve with the yellow coil. Reconnect the power, use a pan to catch the water and press the dispenser lever. If water comes out slow the valve will need to be replaced. If it's good then this will be a process of elimination to determine what is happening. Take the line loose at the connector under the freezer door. Use a pan to catch the water and now activate the dispenser lever. If the water comes out under pressure, the problem will be with the line in the door. If it's still slow the next place to check is at the reservoir. Take the line loose at the outlet end of the reservoir and press the lever, if the water is slow reconnect it and check the inlet side. If it's good replace the reservoir, if it's also slow the next place is the filter housing. Again make the same checks at the outlet and inlet. If the pressure is good at the inlet but not at the outlet and you have already replaced the filter, then the filter housing will need to be replaced. This can be a difficult problem to solve and I recommend calling for service and having a technician check this.