when you add a turbo or a supercharger do you need forged pistons, connecting rods, and crank?
You don't really "need" them, if boost is kept at an average level. Though I'm not sure how long your engine internals are going to last if your boost is up around 70 psi :mrgreen:. Are you talking about any particular car?
what level is average boost?
When you add forced induction into your engine it is always a good idea to upgrade your internals to a stronger set, However, I have seen people who just throw a turbo on their car with stock internals, and only run 4 or 5 pounds of boost.
It depends on the car, a Skyline GT-R could handle more boost than say a honda civic.