fully recirculated depending on what you're trying to achieve. If you want your BOV to
make noise, this unit can be fine-tune to give you that atmospheric BOV sound without
causing a CEL, stalling, or your WRX to run rich.
Besides the noise, why else upgrade the stock WRX bypass valve? The stock unit is
known for leaking and having inconsistent boost pressure that will prevent your WRX to
perform at its best. Moreover the GFB BOV can return the engine to peak boost up to
30% faster than the stock unit when shifting gears.
Overall its a great mod to have for optimal performance.
2008, 2009, 2010, 2011, 2012, 2013, 2014 WRX
2005, 2006, 2007, 2008, 2009 Legacy GT
Fully Adjustable from Atmospheric to Recirculated.