the charger thats on there wont support much over 11 psi reliably so you are going to need a charger / turbo upgrade. from forum reports, injectors max out somewhere around 195 -200 rwkw. TO4 kits are common and not too expensie and probably a better way to go. compression is 8:1 on those motors and they have strong internals, so they can probably fairly reliably support 18psi on standard internals.
intercooling is always recomended.