If he needs one or his tuner needs one .ITS A TEMP FIX,if his tuner is suggesting he needs one ,HE IS A HACK tuner...Bumping up the fuel pressure by the regulator will be take out by the ecu after a few miles of driving it..
ANY stang that is tuned PROPERLY aka chip,doesnt need the fuel pressure adjusted.. As long as the regulator is doing its job,anything else can be tuned out with a chip.
Personally,You should go to bigger injectors and dump the fmu(which you probably have).THen get it properly tuned.
If you tune a supercharged car VIA the fuel pressure regulator ,plan on it running LEAN after driving it awhile..But its not my money going down the drain.