I just got my STi 2 days ago and I was thinking to install BOV on it. Here comes the question. Is it the same on STi as on WRX?

It should be the same. I don't see why Subaru would make any changes to it since it the same BOV used around the world.

The STI and WRX have Differnt Boost Pressure. Whould the BOV be a differnt part?

Blue

Why would you need a different BOV for only a 1psi increase? I checked with a dealership today and it is the same part number as a WRX. I ran 15psi in my WRX and the BOV has no problems with it.

IF you were running more along the lines ofr 20psi then I can see the need for a different BOV.

I'm running a blitz dd with no problems. ;)

Then at what pressure does the BOV activate?

It's adjustable. Between shifts when there's overpressure you'll hear it. Usually above 4000rpm. I think? I left the stock setting alone because the instructions were in Japanese. If anyone has advise on the right ammount of adjustment this it would be helpful to me. Thanks.