The first thing to do is make sure your window sweeps are in good shape and arent causing any issue. Then, make sure the scissor assembly is greased really well as well as the roller track.
After that, as long as the wiring itself is in good physical condition (ie no frayed wiring @ the connectors) then yes basicaly a good relay kit is one which converts the switches to act as ground triggers only and this will provide more voltage to the motors. With more voltage the motors will react faster with more torque and will no donit with less amp draw-at least with my kits they do.