The Goose Honk Killer (GHK) is a kit that will increase the internal spring pressure of both factory recirc valves and this additional spring pressure will only allow the Recircs to open under high vacuum conditions. This is the exact same reason why aftermarket BOVs prevent the Goose Honk and can be vented direct to the atmosphere... because they are not open under idle/low-load conditions, allowing un-metered air to flow into the engine.
The Recirc valves were manufactured as sealed-units, because of this it is not an easy task to increase the internal spring pressure without some way of gaining access to the inside of the valves. Also an obstacle is the correct spring pressure that will keep the valve closed yet allow the Recirc to still function when needed. The GHK takes care of both these issues economically.
By cutting the top of the Recircís diaphragm canister off, the perfect location for the GHK spring is revealed. The GHK machined aluminum cap simply presses onto the canister with some RTV silicone to seal the unit again and the valves bolt back into their stock locations. The GHK converts the Recircs to the best of both worlds, no more annoying Goose to detract from your driving experience, no obnoxious BOV sound because they maintain the stock recirculation plumbing, and the valves still work when needed to vent boost pressure and reduce compressor surge.