Im curious how many horsepower you can get with a stock engine? In that i mean that you dont change anything on the engine, turbos, ECU.

 

Well limiting youself to not changing the ECU is the problem..without doing that the question becomes...what is safe ?..not how much ?

No change to ECU I would guessimate ~ 250 rwhp (some bolt ons)
Being able to change the ECU ~ 350 rwhp (all the bolts ons)

Completely OEM - ~220rwhp

 

Stock hp at the flywheel is 255, if you tacked on intake and exhaust you could probably get up to 300hp without having to upgrade the ECU, however it's borderline because as long as your turbos are only putting out about 10-11 max psi you don't have to worry, but with those upgrades it could spike up to 12-13, which is beyond the stock ECU and could cause your engine to go boom.

First upgrades I'd do are get a boost gauge and controller, fairly cheap and will let you know a whole lot about what your car's doing, or what it isn't doing properly. Then get exhaust, then intake.. and go from there.