this is important: airbags are not a "one size fits all" thing. i cannot stress this enough. I work at one of the top airbag/seatbelt suppliers and we spend 3-4 years on the development of airbag systems for each vehicle. every new vehicle environment is its own very unique animal...
so if you are going to use the seats from the sti, please, don't try to make the bags work!! It is true that having an airbag is much better than not having one, but only the ones made specifically for your vehicle!!!