It all depends on the wastegate, not the turbo.
I'll give a brief run down of some basic wastegate information.
The "gold can" often associated with the internal wastegate setup is what's called the wastegate actuator. There is a spring in there which determines when the actuator will move the arm and open the wastegate. From your info, this spring is a 12psi spring. You change the spring, or to an actuator with a different spring, you change when the wastegate opens.
Did you understand taht last sentence?, because that's your answer.
If a dumbass tells you that you can turn it down with a boost controller, kick them in the nuts and never listen to anything they have to say ever again.
You can always run an external wastegate and solve everything, the downside being more money and more work.