Originally Posted by opto_isolator

You are forgetting something. What happens when you boost? You put pressure into the cylinder head. You are creating a pressure differential. The cylinder head is normally at VACUUM when driving, pulling fuel into it from the injectors. When there is pressure in the cylinder head, you are causing LESS fuel from the injectors to go into the cylinder head (granted you are still getting fuel, but its LESS because of the 5-10 psi of boost or whatever you are running). That's why you NEED an external boost referencing FPR! If you don't run with one, and ONLY rely on the FPR in the tank, your fuel pressure will NEVER raise to compensate for the boost pressure. 1:1 - for every 1 PSI of boost pressure you add, you need to add 1 PSI of fuel pressure to compensate - keeping your fuel trims equal across the board. This isn't going to damage your injectors OR fuel system, as the static pressure across the injector remains the same as it did without boost.