There's a company called QT (Quick Time?) that makes a cutout valve but it's big and bulky and the actuation is slow. I toyed with the idea of taking an exhaust valve setup from a C6 Corvette muffler but it just isn't worth the effort. If you want selectability just get the genuine PSE. A used one goes up for sale once in a while. Otherwise Suncoast lists it for over $2,000.