Y0880 - On the GTR you can run up to 1.4 but not if you intend to keep your turbos for a long time. I'm running 1 bar and have been safely for a while now and I think anything between 1bar to 1.4 is risky with the standard ceramic wheel.... especially in summer.
71LLA:
It is a small metalic ring that sits inside the vacuum hose on the way to the solenoid which restricts your car to the boost it runs stock. Hence the name
You pull off the vacuum pipe, and get pliers or tweezers and pull it out and reattach the vacuum pipe. Alternatively cut the part the restrictor is in (you can feel it).. and reattach the pipe.
The boost is not affected by the ECU here and there is no boost cut at this level... when you remove the restrcitor you get instant one bar boost.