On the show Gearz they put an exhaust by Heartthrob on an F150 with the v6 and gained 39 rear wheel horsepower. It's a cat back kit so it's fully legal anywhere. They also used a tuner on it and put a new air intake and gained more power and better fuel mileage. If Ford ever gets the new van here that would be a nice upgrade for it if/when the parts are available for the van. At the very least the tuner should work since it's a standard OBDII connector.
http://www.heartthrobexhaust.com/
http://www.heartthrobexhaust.com/