This is almost the same problem Im running into. I have a deadhead system in my truck but Im trying to convert to return style. The deadhead system has the FPR in the tank with the pump. The bypass is run directly off the pump and variable voltage is used to control the PSI of the pump to the injectors. Currently my pump key on spits 50PSI, running it shoots up to 60PSI. During WOT, I get a 2PSI drop for a second, then it raises back up to 60. This site will help you see more of what Im talking about. Im taking pics of my intake when I get off work today and posting them on the thread I started yesterday to see if anyone has any options or suggestions to throw at me. I know this thread is a little old but just in case someone runs into the same issue, this might help a bit.