Free Flow Exhaust

Today's exhausts are restrictive and waste power and therefore gasoline. Why don't we use highflow catalytic converters and dual exhaust on all V shaped engines to maximize power and MPGs?
Ron J 04/26/2011
Everyone seems to add dual exhaust on their pickups, why not add that as a factory option? It's as much a "fashion" statement as a power/fuel saving measure & would give Ford more $ in the bank! I know I would check that option box.