Best GOOD and CHEAP BPV for our cars is free - the stock one. Welcome to the board. Take some time and read the threads on BPV's and on intakes, for starts. Believe me, the stock BPV is extremely elegant and well made on our cars. Replacement BPV's never make more power unless you can prove that the stock valve leaks, and they seldom do.
The way to have noticeable sound from your BPV is to upgrade the intake. Yes, that's what I said - the INTAKE. The stock air box is designed to absorb or cancel out all sound it can. Put on a simple inexpensive SRI type intake and I'll guarantee you that you'll hear the BPV just fine. And, because the stock intake is so restrictive, you'll find that you get a big jump up in power (typically 10 to as much as 20 whp) with simple intake upgrade. You need to do this anyway, so why not spend the money where you'll increase performance. The added benefit is that you will easily hear the BPV release. I prefer CAI intake, but SRI will do you just fine. I'm not getting into the debate about which type of intake is better. There is no clear answer, other than this: ANY good aftermarket intake from a reputable manufacturer will produce really significant power gains and give you the BPV release sound you are looking for.
Last thing: Take everything you knew or thought you knew about the STI and throw it out of the window. Our engines do not respond to mods or tuning in the same way as other cars. And true BOV's are an absolute NO-NO with the stock ECU on our cars which have MAF controlled ECUs. If you vent to air, you are taking air that has already been metered that the ECU is expecting to enter the combustion chamber and which it has already measured fuel to match. When you fart that metered air to atmosphere, the ECU does not know this and commands the injectors to spray the cylinders with fuel to match that missing air. End result, you run rich at least during shifts, and typically have rough, uneven idle and low rpm throttle response issues. That air needs to be recirculated back into the intake to maintain proper AFR. You cannot properly run a vent to air (VTA) BOV on our cars without a custom tune from Cobb Access Port to compensate for the missing air during the time that the diverter valve is venting.
I mean no offense, and hope that you find this information instructive. Again, stay around, read and learn. This is not a Subie you are driving and all turbo cars are NOT alike.
