A lot depends on their mileage and how they've been looked after and serviced. If it's done over 250k kms it would benefit from a freshening inside.
For the boost, you have options of fairly high priced valve bodies or $140 Transgo shift kit to get the pressure up if you're mechanically capable.
They need a good big trans cooler and synthetic fluid. Temp gauge highly recommended so you keep an eye on things. Heat is the killer..
They are a tough transmission if serviced properly, nissan also used them in the 224kw twin turbo Z32.
Im pushing 300rwkw through a std one and it still works. A big trans cooler is a must as John has pointed out.