You will not support 290 whp with a t25...
A lot of people down the top mount but its a decent intercooler if you actually get air flow to it. I suggest tilting the intercooler up at an angle to channel the air through it using that wrx scoop.
Multiple runs this way... on 14lbs, a/f stayed below 11.7:1 @wot on 4bar, hot side was hot, cold side was COLD, and I was very suprised.
I rocked the top mount first in its stock position and it would be steaming hot, always, even on cold days... went to a large front mount and piping for a while - sold my piping to a friend that needed it, but last year went back to top mount for a little bit suspecting a turbo upgrade. I tried tilting the IC up and to my suprise it healed the heat soak issues that so many people spit about. 4 bar and a little bit of raised pressure will be good.
In order to tilt the IC you will have to get a U pipe and cut it in half and extend it with a coupler... and bang bang...
Stock Mounting... try and stay under 12lbs, and feel the IC after... cold side was always hot even with the hood scoop.
Tilted up... Made world of difference... 13.6 @107.1 on 13lb stock setup w/ a 3" exhaust... cold side would be cold