How do i turn up the boost on my stock turbo on my mk3 supra? i want to run 12psi. How do i get it to that point?

what mods have you got to your engine? have you done ur head gasket yet?
if you have any mods and turn ur boost up to 12psi you will most likely hit fuel cut and if you haven't done your head gasket you will most likely blow that :P

you can shim the wastegate with washers or buy a manual boost controller and follow the instructions to connect it up... i would say run 10psi so you don't hit fuel cut and also start saving for that head gasket ;)