well BOVs are more relavent for vehicles with high pressure
turbos, because these turbos need more exhaust pressure to start
spinning. when they are not spinning they lag, and when u release
the accelerator pedal abruptly, the exhaust gases backflow. This
backflow exerts a back pressure on the turbo which will cause it to
slow down or stop. This translates to turbo lag, which is
undesirable, so a BOV prevents backflowing exhaust gases from
having an effect on the turbo turbine by venting it out of a
valve.
