[Supras] Plenum valve

[Bill]

Hey, I know I just have a dorky little N/A with no boost, waste gates, etc. But what is the function of the valve that opens and closes in the plenum that divides the chamber in two, by way of the mysteriously named "actuator?" Some kind of torque enhancement thing? Also, it's connected to the vacuum reservoir on the port side of the engine. My valve had fallen apart inside, so i took it apart and put the valve back in, making a little retainer to do so. When I test this vacuum reservoir with a hand vacuum pump, the check valve in it leaks down, after maybe 10 seconds. Is this right?

Thanks,
Bill