I currently have AP Stage 2. After dyno day (i got 223HP & 227 lb/ft), i realized that i still can have plenty of extra horse safely. I'm going to put high flow 3rd cat (still don't wanna kill trees), JDM STi TMIC, and maybe Deadbolt PnP stock turbo. If i add ecutek, i'm pretty sure that i can have 250HP and 260lb/ft with lots of low end pull. That's my NEW goal. now.
i got a hi flow cat... and mine still makes decent power... from what i hear, having one high flow cat will not make u lose much power