As per Maxitrol, brakes first as you'll want to be able to stop. Then exhaust, maybe a clutch if you're going stage 2 hybrid mine needed replacement shortly after fitting a stage 2. The fuel system (injectors and pump) and intercooler will deal with a stage 2 without much issue, but the intercooler would be worth upgrading at some point.
Give me £500 and I can ship you a CR Turbo stage 2 hybrid that has not been fitted.
Fish