Fuel System.

At what point should you start upgrading the fuel system. After what PSI? Cause i think a read a while back that somebody was running 13.5's with the stock fuel system? i mean injectors pump and stuff.

If you upgrade your turbo, you are going to need to get more fuel flowing to use it's full potential. It's not about PSI, but airflow. You can run a T25 at 20psi and have enough fuel, but stock injectors won't cut it with a 16g at 20psi.

you can upgrade everything but your fuel injectors when ever you want. fuel pump, rewire, afpr. but as soon as you get larger injectors you will need a fuel controller gmmaft, safc, vpc, emanage, dsmlink. anytime the ecu sees more then 7 bits of airvolume you'll be hitting fuel cut. that just wont happen with the t25, it dosent flow enough air for the ecu to restrict fuel.