I will set my fuel pressure at 38 then I will reconnect the vacuum line and drive the car. After about 15 minutes of driving I will recheck the pressure with the line off and it will be back at 45. Does anyone else have this problem? How can I keep it set where I want it?
Off the top of my head, I'd start with small things like looking for kinks or dents in the return line. Have you made any other changes to the fuel system?