You said you "know very little about cars", so I'm going to tailor this response based on that information. The prices I'm listing are for parts only. If you're not going to DIY install, consider the $100/hr labor rate that is going to be factored in, and add significantly to these prices...
To add an EWG setup to your car, you would need the following (at a minimum):
1) New uppipe
2) Wastegate
3) ECU calibration
You're looking $1000+ for that to be done.
Of all the years of WRX, 2008 is the "black sheep" year that they were produced. Unless you only care about sound (not bang/buck), you really should be looking at a new turbo (e.g., VF52 takeoff from an '09-14). You can install an EWG on a VF52 turbo too, so if you're going to go that route, make sure you spend the money wisely. You would be looking at (in addition to the other three items) while you were there:
1) New turbo
2) New turbo inlet. Factory inlets are known for failures, so while you had the turbo out of your car, you should replace the unit with a silicone unit that isn't.
3) Aftermarket boost control. You're having to retune all the boost tables anyway, may as well add a more precise method of boost control.
That just added $300-400 for #2/#3, before even considering the cost of the turbo (do you go with a used take-off, go aftermarket, etc.). You'd get better ROI from these three plus the calibration vs throwing an EWG setup at your stock turbo (you wouldn't need the aftermarket boost control, so you could save yourself $100 or so there, but you'd be retuning the boost tables, so you should include it in the build).
Here's where other items come into play:
1) Intake. You're replacing part of the intake tract, you're doing recalibration, you should consider an intake as well at this time.
2) Injectors. Your factory injectors will be at their limit with a new turbo, so you should really consider going with larger injectors for additional headroom and/or the ability to add E85 fuel into the mix (additional ECU calibration charge).
3) Fuel pump. You will need a better fuel pump to adequately supply the new injectors.
4) Intercooler. The plastic endtanks on the OE unit are known for having issues. With the additional power you're going to be adding, you should be considering a replacement unit, which, if chosen properly, will add more power, more safety margin, or a combination of the two.
5) BOV/BPV. If the valve on your car is a crappy unit, or hasn't been properly setup/maintained, it's leaking.
6) Gauges. You want to be able to monitor what's going on with your vehicle. Because you're using it to monitor for issues, you shouldn't buy cheap gauges, so factor in $200/gauge plus pods to house them in.
There's another $2000+
Do you have a "safety net" fund for if the motor takes a crap? A new shortblock is ~$2K from Subaru, then another $1K in other parts to replace while you've got the motor apart, assuming there isn't damage to the heads.
tuapola93 said:
Clueless about what that means lol i want a wastegate cause of the sound. Always wanted it, just don't know what the difference is between external and internal yet.
A wastegate is used to bypass airflow from the turbine wheel to help regulate boost. A turbo builds boost based on the exhaust gases that are coming out of the engine.
The difference between internal and external wastegates is where you're bypassing the exhaust gas; internal is in the turbo itself, external is prior to it getting to the turbo.
TL;DR: Really do the math on what you are willing/able to spend on the car. Don't get me wrong, an atmospheric-dump EWG is a fun sound. The issue is that it will not really help you without a bunch of other supporting modifications, and that makes your car like the regular Japanese econobox (e.g., Honda Civic, Toyota Corolla, Nissan Sentra) with a fart can: a joke.