ive been doing soem research and it seems pretty easy to get a supra to boost at 13 psi from the stock 6.5 psi. im just wondering how much horspower it would have boosting at 13 as opposed to the stock 220h

I would be less concerned about the HP increase and more concerned about how long that 15+ year old turbocharger is going to last doing twice as much work. On the stock ct-26 the old saying is roughly 11hp per psi, but that can change tremendously with the condition of your engine, turbo, and everything else involved.