Cold start idle?

Hi...... What is making the engine run at high idle when cold? (Choke as it whas on older cars.) 1988 E150 302 EFI. My cars idle seems to go down to fast at cold. Then it nearly stalls, and
then goes up at idle again.The first 3-4 minutes when start at cold it idles high and fine as it shall do. The problem seems to be from that time and until it's warm. Runs fine at idle when normal operating tempratur. Have replaced for other reasons Upper intake manifold gasket and IAC. (Because I had high idle at all conditions. And that helped.) Have also had a troubble code from the EGR valve not closing sensor, but that went away when I cleaned the EGR from carbon builtup. Could it be the EGR valve that is worned out from all these years? Or is it any vacum valve that controls this? Janne....
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