have 500 efi's in my boat, warmed up to 625, but have stock fuel system. Stbd motor will randomly jump from 60 to 90psi on gauge, at lower RPM's, idle to about 1500. When it does, motor does run rough, like its loading up. If I'm up on plane cruising, 3000-3500rpm, it drops back down to 40PSI and runs fine. If I push it a little harder, it will start to creep up again, but not all the time. Cool fuel was replaced a couple years ago, pump and regulator. Over the winter, before i put motors back in, I had injectors sent out, replaced all vacuum lines, and cleaned both screens in the regulators. Filters were replaced too at that time. Any thoughts??

I'd start with replacing the regulator