Needs to have the full pressure tested.....ie...best place to do is 5th injector pipe removed and connected to gauge able to read up to 100psi.....Fuel pump relay plug terminals 30 and 87 bridged....Pump will run .....pressure should show 85 / 90 psi....this pressure is maintaind by the pressure regulator....located looking from the front of engine ...right hand side..at the very back of engine..its a normal looking regulator...BUT has no vacumn pipe on it...nor should it ever have....needs full checking... is your Tuner well up on these RS system