Bigger turbo… plan on a bottom end first.
And the trans as mentioned doesnt like to hold good power for very long getting hammered on.
IMO, its clean as shit it seems, it wont ever be a blistering fast car without $8K under the hood and next to your right leg. Leave it as it is, get it tuned if you think its not running well as it sits moded and put good suspension on it. AutoX, track days, and romp back roads with it. A good driver doesnt need 450awhp to have fun in a car like that.