97 suburban idles rough on initial start up.

I have a 1997 Chevrolet Suburban with a fuel injected 350. Whenever i turn the vehicle
on it  acts as if it is running out of fuel and spit and sputters.  I can push the gas pedal
to the floor and it backfires.  It only used to do it in the mornings when i start the
vehicle but lately has been doin it on every start up.  I have replaced everything from
fuel pump (two pumps and last was entire module assembly) fuel pressure regulator,
IAC valve, coolant temp sensors, o2 sensors, tps sensor, and basic items of course
are plugs, wires, cap, rotor, and coil.  I have asked around alot and i get the same
awnser being a bad coolant temp sensor but i figured i couldnt have that bad luck in
getting 4 bad sensors in a row!