Hello. I've got some problems with fuel delivery on my next configuration:
  • 360 N/A stroker Magnum, about 500 HP.
  • Holley EFI Terminator.
  • 12-890 Holley fuel pump.
  • Holley 100 micron fuel pre-filter & 10 micron post filter.
  • 12-846 fuel pressure regulator installed after fuel rails.
  • -8AN line from tank to pump, -6AN feed line to Terminator & -6AN return line from regulator.

So at this point, FPR set to 43 psi at idle (with disconnected vacuum line). It works fine and keeps this pressure for about 2000-2500 RPM (with connected vacuum line pressure is about 38 psi). After that, at higher RPM pressure seriously drops to 15-20 psi sometimes to 6 psi. When pedal pushed abruptly on neutral, I can see the same thing.

I've already changed the fuel pump to another brand new 12-890 from box, installed fuel pump relay, pump feed & ground now directly from battery, installed another new FPR, check & clean all the filters & fuel lines, nothing happened. I also tried to feed pump with gas directly from canister. Voltage on alternator is about 14V. At this point, I've dismounted Terminator throttle body, check fuel rail lines, but they are good. Really don't know what to do now, already have a headache from all of it. Can you advice something to me, what I have missing?

P.S. Few months and about 500 miles ago, there was same configuration on this car with only 12-600 fuel pump, and pump feeding from Terminator. All other parts were same and it has worked good, without any fuel problems.