It's not likely that one of the high pressure fuel lines got clogged. Fuel goes through one or two filters before getting there, a very sensitive pump and the pressure is really, really high. Lower fuel flow on that one line could indicate there is still air in the system working its way out. Is that particular line kinked/damaged?
I had an universal XP-25 on a previous boat and I don't remember having to crack injector lines to bleed the system. Matter of fact, there were some who advocated leaving one of the bleeder knobs openned all the time, so it was a self bleeding system.
This is m-25 maybe a different engine. Only have one bleeder screw on pump.
Yes I agree that it seems unlikely that a high pressure fuel line could get clogged. But at the same time I was surprised at how it was to blow through the line with the line removed. I'll try the breath test on another line. If its not the same something has to be up.
There is a little ceramic type material that has rubbed off in one place but that is about it.