I am seriously NOT a mechanic or subaru specialist in any way. I have been driving STI's and WRX's since 2000's, but never really considered these little parts that contributes to making a difference in the long run. I always believed big parts such as aftermarket turbo or bigger parts made a difference back then. But since getting the 22 wrx (and not totally satisfied with it at first with all stock parts), I started researching more on small parts that makes a difference (to keep my warranty). Now mind you this part is in combination with carbon filter removal and Grimmspeed dry con air filter. Stock exhaust except ETS axleback exhaust for further clarification. Not just the radiator cap alone.
Yes...this increased pressure from factory to 1.3 bar DOES make a difference. The idle rev is a bit more powerful, and the PSI on the turbo did increase a bit after installing this. I am a true stickler when it comes to observing performance on stock parts vs. aftermarket parts.
It's a worthy investment.
Again, thank you SubieMods.