theres lots of potential as proven by this video: 1/4 mi run http://www.paddy.co.jp/democar/hkssuperdragmeeting.wmv
dyno vid http://www.paddy.co.jp/powercheck/DEMOCAR_S13.wmv

its a 650hp ca18det

i have no first hand experience, but evidently the stock internals can handle around 400hp. what else do you want to know?