Fuel injectors Si

okay i had a leaky injector on my 89 si. picked up a set of HF injectors for free. Was curious so i flowed the HF's in the flow bench. After thirtry pulses i got 30 mL of fuel. So, then I was more curious what the stock Si injectors flowed so I pulled them, out the car and did thirty pulses and got 40 mL of fuel. So I decided not to run the new HF's because it would be way to lean and probably burn the piss out the motor. So I decide to run stock Si injectors. But then I remembered an old buddy with some B16 injectors. More curiousity mayed me flow test them and in 30 pulses I recieved about 51 mL of fuel. So I'd rather be rich than lean so I put the B16 injectors in the 89 Si hatch D16A6 motor. Recet the ECU of course. Gas mileage is down a bit, as expected, performance slightly higher than expected as well. No O2 code present. Good to go. Question these injectors cannot be flowing all the way with this pm6, stock pressure regulator and rail. What, if anything can I do as far as regulator/rail/ecu to get more performance out of them not minding the fuel milage? Anyone know?