Originally Posted by nauli

Basically I wouldn't touch any of the pads you've used.
I assume you installed them yourself...did you put the anti squeal plates/shims back with them and did you bed them in? All new pads need to be bedded in and there is a process for that...you shouldn't just chuck 'em in and drive off.

I used Pagid RS yellows (with DBA 5000 rotors) when I had the '06 STI and they rarely if ever squealed and they are a competition pad. A reasonable street-performance compromise would be something like a Bendix Ultimate or a
DS2500.
Often the squeal can be set up by the driving style glazing up the rotor and pads. I suggest you seek advice from a reputable Subaru workshop (not dealer!).