94 chevy k1500 5.7l stalling, bad gas millage, and hard to start

Truck stalls when hitting the gas at idle and in gear
unless you ease into it.  Only way to get it to start
again is to crank it over with the gas pedal pressed
all the way to the floor. Hard to start when cold and
at running temp. Need to put the gas to the floor to
get it to start. The truck will run normal every once
in a while but doesnt last long and will still be hard
to start. Also idles kinda high when its running
decent. Throws a rich o2 sensor code, egr or
barometric sensor code and an idle air control
valve sensor code. I've replaced the o2 sensor, egr
valve, injectors, fuel pressure regulator, fuel filter,
Plugs and wires, idle air control valve, tps, and  
looked for vacuum leaks found none. Any help will
be greatly appreciated