[SteveYem]

I can’t really say by looking at the image on the first page, but I would guess that by default when the valve is closed. The exhaust gas is routed through the muffler and distributed to the other three outlets….unless the two inner outlet pipes on each side are just for show, which I doubt.
If I’m right, then exhaust gas would flow out of both sides of the rear of the car at startup when the valve is closed, which is an improvement for anyone irked by the stock exhaust configuration in this respect.