MIssfire under Boost

[mdprovee]

Hello and hope you can help. I have a 383 SBC with Fast XFI 1.0, Holley Stealth Ram, and P-1SC Procharger. I have a MSD 6AL box and MSD Coil. I dont know alot, and have been chasing a problem. It just started within the last year. It runs great from idle to when boost starts. Once the boost kicks in (about at 4-5 PSI), the motor starts to misfire and cut out. I have replaced the cap and rotor, plug wire and gone thru several sets of plugs. Any ideas I can check? Thanks for your help.

Mike