Its depends. On the Mustang near me you would be looking at somewhere in the 270-280 range, maybe slightly less. Dont be sad, it takes a 20G+FMIC and 22PSI to break 300whp on that dyno, and stock STIs make @210whp.
Most Mustangs read a little higher. The BIGMAF will get you nothing if you arent maxing out your stock MAF, and with that turbo, no headwork or cams there is almost no chance you will.
A TurboXS/Perrin/APS tmic will make a good bit more power than the JDM STI tmic, honestly the JDM STI tmic is barely any better. Its the exact same core with like 3 more rows. That only makes it flow a LITTLE better, not cool any better to speak of. The power difference between that and a USDM sti tmic is pretty close to impossible to measure, and is well within the error of margin of a dyno.
You will make a little more power on that setup than you would a comperable single scroll setup, so compare it that way. You will however, make a lot more low end power and have better throttle response, slightly better than the 2.5L single scroll STI.
22PSI will be ok, but its pushing the limits of that turbo, sort of. At 22PSI I would absolutely recommend the SMC meth kit, but you dont need to spend the money on 850cc injectors, 750s will be plenty. Especially with the meth.
SMC is gone, and the AEM kit is cheaper anyway and has a few more and nicer features (including they VERY cool new pump system)
A FMIC is ALWAYS going to outperform a TMIC, but a quality TMIC will work very nicely with your setup, and is a little more New England winter friendly. TurboXS's tmic is cheap too, while still having a very nice core. Sell the JDM sti tmic and it offsets that cost a LOT.
I would HIGHLY recommend running copper plugs. You will only get say 10-12k out of them, and many people recommend replacing them when you do oil changes (3000-3500) but they are dirt cheap and have a stronger spark, that will hold up to the high boost better. I have yet to see a platinum or iridium plug outperform, or even perform as reliably as a copper plug. Plus you can run a stock heat range copper, which will perform better when warming up and I believe low rpm light throttle and cleaner emissions (dont quote me on that part about low throttle and emissions) Because a copper plug by its very nature will perform like a slightly cooler plug when compared to an iridium or platinum.
I would go with
AEM alcohol injection kit
22PSI (Actually, I would do 23)
Replace everything in the intake tract in front of the turbo. You dont need a big maf, but if you can get one cheaper than a normal sized one, go ahead. Its not needed but it wont hurt anything.
I definitely wouldnt count on 330whp, and would place you more in the upper 260s, but trust me, it will be VERY fast, capable of an 11 if you drive it VERY well, especially if you drive to NJ and do it at ATCO. On a dyno like Andrewtech/TurboXS has, plan on 330-340 easily.