| :they allow the turbos to maintain maximum spin between shifts (quicker post shift recovery) Actually they do more to prevent damage to the turbo than to help spool. My old Z had no BOV's or recircs, and it spooled up just fine. The BOV's bleed off excess pressure preventing that pressure from backing up back into the compressor wheel. The more air you bleed off, the more lag you'll have since you no longer have any pressure waiting before the throttle plate. When I adjust my BOV's too loose, they bleed off too much air and the turbos feel laggy after each shift. If I make it too tight, they don't let off at all, but there's plenty of power after the shift since the pressurised air is still there waiting to be let in by the throttle plate. Setting it just right enables them to bleed off some air without releasing all of the pressure. Think about it, if bleeding all the air off wasn't a bad thing, they would just design them to be non-adustable and bleed all the air off until there's no positive boost left. But they make them to be adjusted, so there's got to be a benefit to not bleed all of it off.
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