Is 20% UNDERDRIVE POWER PULLEY KIT FOR FORD any good for everyday driving?

This kit basically increases horsepower by reducing parasitic power loss from driving engine accessories. For street use, you should rather have the added comfort of knowing that the alternator and water pump are running at factory spec. If you were making a serious or semi-serious street/strip car where it wasn't a daily driver then yes. But if you were looking for a little more oomph out of the everyday car, you can look at other options.