Everyone knows how a BOV(Blow-Off-Valve) works! On the WRC its always making a sound like a BOV but many times in a row. I dont know if this is a Sequential BOV or the Wastegate. Every single time the WRC changes its gear I hear that sound! Then I say WTF I want that on my WRX. Does anyone know what this is?

From my understanding it is a resirculating Turbo and part of the anti-lag system they run. basiclly it keeps the turbo spooled so the waste gate open to keep the boost at the level they want.

so as for getting it on you wrx i think it would be more money then you have ever wanted to spend.

you may find this helpfull

http://www.rallycars.com/Cars/bangbang.html

Erik S.
Car 463

its an open wastegate... the wastegate opens at a predetermined boost level and vents it making that noise. the wastegate flutter is barely audible on a stock or a near stock WRX (you really have to listen for it) but when vented externally, you get that sound like the WRC cars.