for anyone wanting to compare a race car with no bov to a road car, consider the following-
using qld raceway as an example, a race car will lift of from wide open throttle 6 times (there's 6 corners isn't there).
now if you take your car to the track, on a flying lap, from the start of the straight to the start of turn 2 you will have lifted off the throttle more times than that. race cars don't lift off on gear changes. most don't even use the clutch.
so why would a race car need a bov? the slowly wind the accelerator on just after they turn the car into the corner, so if there is any extra lag from not having a bov, it doesn't worry them as they don't really have any on/off throttle aplications.