well looking at buying a rst for the runing gear but it has a issue, one ive not come across before,

right mfi rst, will start on the 5th injector only and dies seconds later, fuel to the metering unit but nothing at the injectors, lots of fuel pressure, changed the metering unit off a running car, tried ecu's, dizzy, changed filters, accum, fuel pump, checked the sensors on the back of the inlet, changed injectors etc, will run if i pour fuel into the metering unit though??? checked for air leaks, only thing that hasnt been changed is the loom. anyone got any ideas?? dont want to buy it and be forever chasing the issue

cheers