My question pertains to the heat valve on the standard IV with the TSIO-550. The valve has 3 positions: 1. Off, 2. Defrost, 3. Heat, and is controlled via a cable from the cockpit. My question pertains to the "off" position - why do we dump the air from the turbo aftercooler sonic nozzles with the valve in the "off" position? The normal install has a hose that directs the bypass from the "off" positon overboard. It seems to me that capping the discharge would not cause any problems. I would like to hear any comments regarding blocking the bypass. Many thanks.