These are the parts I recommend. I recommend them because they work and the companies actually care about the Subaru community.
* Cobb does not make Stage2 CobbSF+TBE OTS maps because these cars are out of fuel with just an exhaust. If you want to set the car up properly and be able to take advantage of the additional parts you've added beyond a turbo back exhaust, then you absolutely need ID1050x injectors and AEM320 fuel pump. And at that point you're an ethanol sensor away from picking up another 40whp....so it makes sense to just get the flex fuel too.
* I do NOT recommend a catless exhaust unless you get an external wastegate OR Cobb/ID1050x injectors and an AEM320 fuel pump. Without these mods you chance running out of fuel, leaning out, knock knock boom.
* I will NOT tune any injectors besides Cobb or Injector Dynamics. It's an exercise in futility to try and make a car drive well with crappy injectors.
* If you are running a FMIC, cams, or plan on making 500+ whp then you should plan on going speed density. Speed density is fueling based off the Manifold Pressure (MAP) sensor vice the Mass Air Flow (MAF) sensor. The 10-15 feet of extra piping for FMIC's can cause fueling issues on MAF based fueling. Cams can cause various fueling issues that can only be corrected with speed density. High hp setups require a large MAF housing which ultimately leads to poor idle and cruise fueling due to the large size of the housing and small size of the MAF sensor.
* 02-07 WRX/STi's need an AEM 3.5 bar MAP sensor or Cobb 4 bar MAP sensor to run more than 20psi. The stock MAP sensors on these years can only read to 23psi.
Blouch Dom 2.5xtr w/ 10cm turbine housing
FP Green or Black
Quoting power numbers is tricky. Everything on the car matters. One big thing people never think about are brakes and wheels/tires. If you put bigger brake rotors and bigger wheels/tires on your car, you can lose 25-35whp from the extra rotational mass. I put a 20whp window on the numbers for this reason...and even then you may still fall outside of it.
Stock STi 240-260 tq / 240-260 hp
stock+Tune 280-300 tq / 250-270 hp
TBE + Tune 290-310 tq / 270-290 hp
TBE + TMIC + Tune 300-320 tq / 280-300 hp
TBE + TMIC + EL Header + Tune 310-330 tq / 290-310hp
TBE + TMIC + EL Header + ID1050x + AEM320 + Cobb Flex Fuel + Tune 360-380 tq / 330-350 hp