No, it won't run cooler but the engine will be ingesting cooler air through piping that has has less losses. Cooler air is denser air, with more oxyen per unit volume. This will equate to more power. Using 2.5" or 3" piping with smooth radii and using a cone-style filter will reduce pumping losses and add a bit of power.
If you get a lot of rain or standing water in your area, be careful which one you choose (i.e. how low the filter hangs to the ground...water is not compressible and since one of the strokes in a 4-stroke engine is comrpession, bad and expensive things can happen when the engine tries to compress a liquid that isn't compressible.)
You can make your own with bits and pieces from Home Depot (PVC piping etc) or you can try:
www.hotshot.com
www.prmracing.com