I was chatting with Graham Hatherway this afternoon and he thinks that BOVs are for idiots who know FA about what they are doing, and that is putting it mildly as this is a family friendly forum
When the BOV releases the intake pressure it removes the air resistance from the compressor thereby allowing the turbine to suddenly speed up. Sudden changes in RPM is what does for turbos, snapping shafts. A properly set up engine with a decent ECU doesn't need a BOV, a waste of good money and BAR, or so I have been informed.
There will be no BOV anywhere near my engine -) When racing I will be full throttle grear changing so the last thing I need is a sudden loss of intake compression!