My throttle bodies have billet fuel rail thats open at both ends, My question is whats best to keep fuel pressure constant throgh the rail.

1: Flow through the rail with regulator on the return.

2: T off the fuel line before the rail with regulator on return leg and blank of the return end of the rail.

I've seen borh ways used but is there advantages of one over the other?

cheers

2.0 zetec R6 bodies and injectors.

flow through keeps the rail 'clean' a blanked end can cause deposits to build up and eventually clog injectors, especially on low use cars...

I have option 2) with my T just after the fuel pump. It works fine, but I suspect you'll get a more even pressure at the injectors with option 1 and the pressure regulator at the output end of the fuel rail, as opposed to the regulator being at the start of the fuel line.