It's possible that different years idle differently.
My 06 in stock "tune", idle speeds will rev to 2200 (or a little more) then slowly come down to the final rpm when the ECT reaches 170F.
I've gone in and commanded at least 500rpms lower rpms at temps above 20F. (20F and below I've pretty much left alone so as to keep fords design intent)
As-is I now start it up in say a 45F temp and the revs will go to 1800 for just a second and then settle into a 1300. Then as ECT temps raise the RPMs drop.
btw, there are several things that the PCM looks at before it commands a certian rpm.
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