Electric choke in sub freezing temperatures

[pennyman1]

you need to adjust the fast idle speed if it is stumbling when cold off idle. It is the screw that rides the cam on the choke linkage.

[MrPaco]

you need to adjust the fast idle speed if it is stumbling when cold off idle. It is the screw that rides the cam on the choke linkage.

A friend suggested the same thing, was hopeful this would be the issue. It might be related to this, but not as straight forward as I was hopping.

I followed the service manual steps to test and adjust the fast idle, the results are a little confusing.
I disconnected the vacuum hose from the choke opener and manually set the lever on the fast idle cam. Turned the ignition on, and engine went to 2,200 rpm, adjusted the screw to 2,300 which is what the manual recommended fast idle speed for my truck configuration, and then reconnected the vacuum hose like the manual says to do, which made the rpms go down to curb idle, 900. I think this is supposed to tell me that the fast idle is adjusted correctly, and the vacuum is working.

I let it sit overnight to start it from stone cold next morning, and the start was still rough, no change.
What's weird is that after about a minute of stepping slightly on the gas so it doesn't stall, the choke seems to engage at that point and keep the rpms slightly raised, but it only goes up to 1,300 and it stayed there for few minutes until the temperature needle reached the second notch on the gauge. Then, when the engine is nice and warm, the rpms dropped to curb idle, 900.
So even though the fast idle is correctly set to 2,300, it never went past 1,300...

Should I try adjusting the idle speed screw while it's warming up (and stuck at 1,300)?