depends on the compression of the engine and the type of gas to use. depends on if you went with okay rods or really good rods. depends on gas ported or not. i'm sure there are other factors but i think that's the gist of it.
On the stock turbo you could easily run 15 psi with forged internals. Just make sure you have enough fuel, and the you are taking enough timing out. Best to buy some sort of ems if you really wanna boost up.
ya make sure u have EMS and larger injectors..you will need larger injectors past 12psi..ive seen people run 15-16psi on the built motor out of a stock turbo..but if your spendin all that money on a built motor you mind as well get a badass turbo.