1996 Chevy Lumina starting problems

I have a 1996 chevy lumina 3.1 v6 when the car is cold below 0 the car starts fine if the outside temp get above 0 you have to push the gas pedal down half way to start i have change the MAF, IAC valve, check fuel pressure it 42 psi, replace Throttle position sensor EGR value tested the MAP sensor and still have the same problem