[Sizzler]

I don't know why the o2 sensor would affect cold-start operation.
During warm up the EEC isn't reading the o2 sensor.

More likely something like moisture in the throttle-cable or in the vaccuum tubing leading to the MAP sensor, or the MAP sensor itself.

It could also be distributor related. Not sure, does that use a TFI module? Though I think problems with the TFI manifest themselves at high-temps, not cold.