GFB is no stranger to dual port BOVs. In fact, GFB pioneered the design in 1999, following up with the patented venting bias adjustment system in 2001. This technology is not just a gimmick – it’s the key to getting a blow-off sound without the issues (unlike other valves), and is exclusive to GFB. When you vent a BOV to atmosphere, you’re letting air out of the system that has been measured by the airflow meter, so the ECU will continue to inject fuel for that missing air, hence the issues with over-fuelling that can occur. However, by controlling HOW MUCH the valve vents, WHEN it vents, and for HOW LONG, the Respons can be configured to vent a portion of air to atmosphere at a time and of a volume that least affects the fuelling to the point where there are no negative side-effects. Unlike factory bypass valves, or other brand valves that require different springs for different boost levels, a GFB valve CANNOT be forced open by high boost! The balanced piston design in a GFB valve uses boost pressure on either side to cancel out the forces. Therefore it doesn’t matter how much boost you run, you can be sure a Respons valve will deliver all of it to the engine.