Well, didn't you test drive it before you bought it?
Anyway, there isn't much you can do with the ST if you want really fast car. I don't know how much performance you are expecting. The best way is to try test drive a GT or GTS first and see if you satisfy with that. If you think they are still slow, now you will have to look into turbo kit or 3sgte swap. Then you shouldn't be disappointed anymore.