mr2 is right, most of them do not run a bov, they just replcace the turbo after every race.
a bov can limit boost, but that is a retarded way to do it.
It's just a spring in the bov, so when the pressure gets high enough it will open. The bad part though is that the turbo will keep spinning making the air hotter than it would be if you limited boost using a wastegate.