your half right, something was mounted incorrectly, the dump valve(this is where you were right), it was the wrong way around. this is never done in error, it is a big performance gain (this is where you were incorrect), think about it. with it plumbed the right way the valve opens and lets boost pressure out. with it the wrong way around (illegal) it never opens and the boost stays on longer and theres more of it. evos have been doing this for years until it was seen by the scruitineers and now seems to very rare. i doubt any of the evo drivers in the country have this done, it might even be the case where the newer evos dont need them turned around anymore, but i'm no evo expert.
N12 forever
N12 forever