Totally agree. I've had my wrx mapped to 285. Also if you are thinking of bigger number you might need to change more than just the turbo. Injectors, fuel pump and most importantly gearbox. The 5 speed is the week point of these cars. I've had mine reconditioned as a bearing had failed. And that not to say it won't go again. Don't get me wrong, they can go to about 330bhp ish, but I don't think I'll risk it. Any more than that then I would look at a 6 speed conversion or sell it and get an sti.
Btw where did you get the fog covers from?
Cheers