MagnaFlow's V-6 Explorer sytem shows a marked improvement over the stock system-thanks to backpressure-reducing, 2.5" fast-flowing, mandrel-bent stainless steel tubing.  The Sport Trac system has an 18" long, 5"x8" muffler, whereas the Explorer benefits from the extra sound absorbtion of the 24" long MagnaFlow.  Both systems are completed with a 3.5" polished stainless steel side exit tip.  Look for significant performance gains of 11 horsepower and 15lb.-ft. of torque for the 4.0L V-6.  These are improvements that you can really feel and hear.