Boost control, stock internals

I have a 1993 Supra , 320 H.P, i was wondering if i got a boost controller and uped the boost would the stock internals be able to handle it? and up to what boost could it handle?

First off, you are thinking in the wrong terms. The idea is to increase air flow, not increase manifold pressure. Simply increasing pressure will not increase output.

Now, the stock internals will hold up to about 500-600 HP. You cannot just add a boost controller and call it good. You will cook the motor unless you do supporting fuel modifications. At a minimum you will need a piggy back fuel computer and an AFR monitor.

I would reccomend that you either start learning about forced induction motors, or find yourself a shop do the work for you.