Ok, Im going to attempt to explain a few things here, keep in mind i'm no expert, and as usual im going to butcher it, badly, but here goes.
Cold start up was always one of the things that took me the longest to get dialed in. You get one shot at a true cold start, then you have to wait for the engine to completely cool down again, usually the next morning.
So, if memory serves me here, you have a "Priming pulse" that squirts fuel into the engine when the key is turned on, like pumping the gas on an old car before you crank it. This pulse is longer on a cold engine, and much closer to the idle pulse width on a hot engine.
Then there is "after start enrichment", this adds extra fuel on top of the calculated fuel needed just after start up, this is usually only for a short period of time, this is timed in seconds or even counted engine revolutions. This is to counter act the cold, dry manifold. There will always be a certain volume of fuel that clings to the walls of the port, it moves along the port with the airflow, but no where near as fast. the colder the manifold, and the slower the engine speed, generally the more volume of a given fuel injection event tends to stick. Just after the engine fires up, the fuel that is clinging to the walls starts migrating to the valve, and within a short amount of time, the manifold is fully "wet-ed" and the amount of fuel that gets to the combustion chamber off the walls remains relatively stable, cycle to cycle. So that's the main purpose of this setting, to account for the fact that, until the manifold is fully wet-ed, it will run pretty lean just after start up.
Then, finally you have Cold Enrichment, or Choke. This acts exactly like a choke would on a carb, it is more tied to engine temp. It adds fuel to compensate for the fact that more fuel sticks to a cold manifold vs a hot one.
All three of these enrichment's taper off as the engine runs longer and/or warms up, but the tricky part is they all overlap each other. Getting them right involves a lot of trial and error, and paying very close attention to how the engine fires up and runs immediately after start up.
To add to the tuning troubles, the A/F ratio the engine wants to run at, at a cold or even warmed up idle, can be a fairly arbitrary number. So watching the O2 can be a great help, but only if you take this into into account. Speaking of the O2, most take a good 30-60 seconds to warm up.
If you just hop in and start the engine, you wont get valid readings till long after the priming pulse and after start enrichment have done their thing.
So turning the key to the on position, then waiting a till the O2 is warm before firing the engine can help.
So, don't get discouraged. For me at least, tuning cold starts was always the trickiest and took the longest. Sometimes i got lucky, and others it seemed i was chasing my tail for weeks.
