1993 Chev Truck no VERY COLD start

I have a 1993 Chev Truck K1500 4x4 with a 4.3L V6 Throttle Body. Problem being when it gets REALLY cold it will not start unless you start touching the throttle. Without touching the throttle it will crank all day. Warmer weather starts 100% and after truch has been starter it starts fine. I have replaced Cap, Rotor, wires, plugs, gas filter, air filter, pcv Valve, O2 Sensor, Coolant Sensor........Please help

Thanks

check for fuel pressure. also check all your vacuum lines for leaks. check vacuum when idling. sounds like its not getting fuel.