Injectors

When replacing fuel injectors, do you have to use all the same brand? I have a 3.1 L. I had one injector replace a few months ago and the other 5 recently. I know that I used different injectors(Borg Warner) than the one my mechanic used(ACDELCO). Since replacing the 5, now the car is harder to start than before. Could the different injectors be the cause?

Any help is greatly appreciated!

Different brands of injectors should not make a difference. How ever, since all your injectors are working now, the fuel pressure regulator or the fuel pump may be weakening. Need to test the fuel pressure.