Adjustable FPR for stock 2003 return style rails?

[HalfCaseKustoms]

Is there an adjustable fuel pressure regulator out there for my 2003 6.0? I have factory return style fuel rails. I'm only reading 50 psi at the rails at idle and it drops when on the tgrottle. Brand new 255 pump in the tank. I figure it's the regulator that's the problem so I want to replace it with something adjustable if possible.