Does anyone know where the restrictor is that helps prevent overboost by flattening pressure spikes to the overboost detector?

I've got a 94WRX with a new full ScoobySport exhaust system.

I've heard that the restrictor is a small brass thing, however all I can find is a plastic one in the hose leading from the inlet manifold to the wastegate solenoid.

Does anyone have any ideas?

thanks in advance,

Steve.