1997 Chevy Silverado engine missfire

I have tuned motor with new plugs wires distrubitor cap rotor new ignition coil new fuel filterand new o2 censor on bank 1. I checked fuel pump for psi when cold it reads 53psi when running it is at 56-60psi would that make motor missfire on start up, only when warm it runs and starts fine.after you start it up in the morning it missfires for about 2-4 minutes code reads multiple cylinder missfire.