Toyota didn't develop a factory Turbo for the 7th Gen Celica motor because the motor can't support it. Companies go with reliability over Performance. They want an engine to last.
High compression motors like in the 7th Gen Celicas can't support high boost, and even low boost will lower the engines life dramatically.
Then again, YOU can take your ride and build the bottom end to make it support boost applications. This usually costs a lot of money... if you want your motor to last