I have a few symptoms of low fuel pressure (poor idle & low rpm driveability). I just checked it at the rail & its got between 32 & 34 psi while running, regardless of rpm. It will spike for a split second when goosing the throttle, but is very consistently 32-34 psi. No pressure past the FPR though. I've looked all over this forum and looked at other online sources but haven't found a solid figure yet. I just regapped my plugs, dialed in my tps and set the ignition timing today to take those out of the equation. The plugs were at about .065 - .070, the TPS was off a bit & so was the timing. Also recently installed a freshly cleaned Z6 throttle body with a clean and tight FITV. All of that made a big difference, but then it got worse. Planning on cleaning the IACV tomorrow as well. My setup is Y5 longblock, Y8 intake and exhaust manifolds, Y8 injectors, Z6 throttle body and P28 ECU. Until yesterday it ran really well except just off idle - 1500 or so rpm. Started throwing codes 1 & 43, for bad O2 sensor reading and fuel system issue. Those codes are gone now, but the problem persists. I'm stumped at this point if it isn't the fuel pressure. As always, I sincerely appreciate all of your input.
Gator

 

 

Thank you. I guess my 32-34 with the vacuum line attached is spot on. I rechecked my timing today and it was 20° or so retarded. I fixed that and its way better now.
Gator