TiALSport springs are engineered for precise control under extreme conditions.
Manufactured from 17-7PH stainless steel, they provide consistent pressure at high temperature, and resist 'relaxing' at temperatures up to 900degF (483degC), well beyond the required temperatures of the actuator.
Springs are color-coded, and are sold individually.
Please see the specific diagram for your specific model, at www.tialsport.com/bov-tech to correlate color coding and diameter in order to choose the correct item.
Q and QR springs are not chosen by positive (boost) manifold pressure rating, rather, should be chosen based on negative (vacuum) manifold pressure at engine idle.