Peace, mercy, and blessings of God be upon you. For sale: Blow Off Valve Hiss. For turbo cars only. Its sound is delightful. It has an adjustment on top. Brand: Forgo. Original, made in Britain. Turbo hose inlet below: 2.5 cm (1 inch) width. Side turbo hose inlet: 2.5 cm (1 inch) width. Used, clean. With the complete set of parts.