What year model is it?
Go to www.wesingram.com/hp.htm and download the Fuel Diagnostics Guide.
It may be that you need to narrow the restrictor to 1/16".
Before you do that, however, make sure that you're getting full voltage to the supply pump (all connections clean and tight and your getting 12v at the pump), that the in-tank boost pump (if installed) is putting out a steady 3 psi of head pressure, and that the tank is vented (no vacuum forming preventing fuel outflow).
Go to www.wesingram.com/hp.htm and download the Fuel Diagnostics Guide.
It may be that you need to narrow the restrictor to 1/16".
Before you do that, however, make sure that you're getting full voltage to the supply pump (all connections clean and tight and your getting 12v at the pump), that the in-tank boost pump (if installed) is putting out a steady 3 psi of head pressure, and that the tank is vented (no vacuum forming preventing fuel outflow).