I would start by making sure the ignition system is top notch.
Spark Plugs, distributor cap, rotor, ignition wires.. I'd check the coil at the same time and maybe a compression check while the plugs are out.
If this does not solve the problem, I'd go to the fuel system:
Fuel accumulator,check valve and filter, good time to check the fuel pump pressure/volume output.
If all this is in top condition you've covered most of the cause of hard cold start.
The cold start valve could also be deffective, but this valve only operates below a certain temperature (I think below 49deg, but not totally sure about that.)