After you do the injector " leak test "
Would it be redundant to do a FPR " test " ?

1) Disconnect feed line prior to FPR { to verify constant flow for a few seconds } Re connect.
2) Disconnect return down stream of FPR { verify consistent return } a few seconds. ( Long enough for pressure to drop? ) Re connect.


Wondering if # 1 would set a base to verify constant flow, then
if # 2 would have appropriate return volume?

Is it possible you got bad // contaminated gas at the station with sediment that found a way to the injectors & FPR?
Just a thought.