Hello all, I'm new here.
Figured this problem i've been having should be shared to the forums. So recently I upgraded my turbo from the APEXI AX53B70 to the newly designed MMP NS400 Turbo. (.86 exhaust and .63 AR T2 stock replacement turbo pretty much.) After changing the turbo, I obviously went to get it tuned. Found out that the fuel pressures were dropping, causing the AFR to go SUPER lean. Fuel pressure would rise up until 6100 RPM and fall drastically to base pressures (38 psi). We changed to DW200 (255lph) and changed fuel filter to Z32 filter. Problem was still there. Left the tuner, installed an Aeromotive FPR, upgrading from the what looked like Nismo FPR. Problem still existed. We decided to run a separate, completely new fuel line above the car, it's own specific fuel filter to the feed. Although it held a little longer, fuel pressure still dropped almost similar. The new fuel pump was hard wired from the start, then hard wire with relay was done directly to the battery since it's in the back. I've ran out of ideas. If this situation has been on here, I apologize and ask that you direct me to that forum with a link.
Upgrades that have been done since but not taken back for tuning are:
AEM 340lph In tank fuel pump
FiveO 750cc side feed injectors.
PS: Turbo was at 18psi, with the 6000 rpm pull, the car made 366 WHP but for safety precautions further tuning was not done. Please guys help me out! Thank you in advance!