The stocker turb (even highflow) will be working so hard to make the boost it will be overheating the intake charge, causing lots of back pressure and generallly making the engine overwork, when a better matched turbo for you power will do it easily and efficiently.
Don't even think about skimping $1000 for the PFC when the rebuild you are rapidly heading for will cost a lot more. I also hope you have a FMIC, and bigger injectors. A little detonation just trying to find the limit can end the ring lands life.
I was making 220rwkw at 14psi with highflow turbo, 800hp FMIC, GTR pump and Malpassi reg, and the injectors were close to the limit so at 18 you will kill it.
I'm now on my 3rd rebuild due to various problems, but the last one was me trying to go too hard without the support systems. Shortcuts work, but in a limited way. BTW my GTR makes 260rwkw with standard everything except a boost bleed and exhaust. Computer must be just a bit smarter.