The Intake Air Bleed function is intended for turbo-charged drag racing applications, where an air bleed valve is located after the turbo-charger to reduce manifold pressure. This is done to reduce compressor load, allowing the turbo to spin faster while staging.
If using a Mass Air Flow sensor for fuel or ignition tuning, the intake air bleed valve should be plumbed back into the intake after the Mass Air Flow sensor. Venting to atmosphere would make the ECU over-estimate how much air is going into the engine, causing it to run rich and interfere with ignition timing.
Output Frequency - The frequency at which the duty signal will operate. Typically a value between 10 to 1000 Hz is used (Default = 23). Choosing low frequencies will create pulsations in manifold pressure because the air bleed switches on and off. Higher frequencies give smoother results.