During a shift the mettered air that has given the ECU the signal for X amount of air being in the motor . BOV opens , no longer the same amount of air for fuel rich condtion occurs , slight spool degrdation .

Its really not worth it to vent it back IMO . The gain wouldnt be noticeable .

Why keep the stock AFM anyway . Haltech or Microtech is the way to go the power gain made by switching to Speed Density is alot .