Has there been a solution to this problem? Seems to be (almost) the same issue I am experiencing in 2019.

My 3.5 running on the 91 tune (U7196, 9r07, 04896411AL CalID) has a very high idle of 2500RPM on cold (30's F) starts. This although settles after +/- 2 seconds to a more resonable 1500RPM ...