1995 Corsica 3.1 problem accelerated from a stop

My Corsica has a bad hesitation from a dead stop.  I press on the accelerator and it almost stalls then it takes off and runs fine through the gears.  This happens from every stop unless I ease into the throttle then it seems ok or the condition is at least minimized.  The fuel pump and fuel injectors were replaced five years ago.  I have recently added fuel injector cleaner, replaced the fuel filter, fuel pressure regulator, knock sensor, IAC, PCV and replaced the catalytic converter(thinking maybe it was clogged).  The SES (check engine) light goes on and off.  I took it to an auto parts store to use their scan tool but the adapter plug wouldn't snap in to the computer port.  I had to hold it on the port while the tool scanned for codes.  It came back with EGR solenoid #1 failure, fuel relay failure and oxygen sensor lean condition.  I wasn't sure if I could trust the codes since I couldn't get the tool completely snapped onto the port.  Would any of these cause my issue?  I don't know what else to try.  Any information would be appreciated.