The 307 is a 255lph pump. It just has some different internals...like a different spring or something...or maybe Im thinking 317 if theres such a thing.oh to clear up
the 190l is the old 307 pump not too good past 65 psi
the 255l is for the 340 pump again better than the 340 but fading fast above 70
the 255l hipsi is the inline walbo
and those are at pump pressures and volumes , doesnt get better through old filters or stock restrictive lines
you can see the diff between 66psi and 76 psi
66 psi = ~45 gallon /hr
76 psi = ~28gallon/hr
By the way, make sure your return line is totally clear and your fuel filter is clean. If the return line is restricted, pinched, kinked or clogged with varnish if the car was sitting, you'll have fueling issues. Its good to disconnect the lines at both ends and spray alot of carb cleaner in there and keep blowing it out with compressed air. Also check for dents or kinks.