Start up on 512TR when sitting for a while

I replaced my fuel pressure regulators on my 92 512TR. I thought this might be causing hard start ups when it's been sitting for a while. Both sides have been confirmed on the pressure. When the car is shut off for a while, I still have issues with cold starts. Car stumbles and have to keep cranking a few times. I get some back firing at times too. Once the car starts it seems to smooth out. My fuel pumps have been both replaced with new check valves too. After I start and then shut off, the fuel pressure seems to hold then after a few hours the pressure drops. I am assuming this is normal? What else do you think would be causing cold hard starts? Injectors?