OK. When I use a plain jane intervalometer I will use camera auto, ISO auto. When using any other intervalometers I use P mode. I use auto ISO if the script can control the ISO or select an in-camera ISO if it cant. That being said I did a little more testing with Meteor 2.4
Camera is in P mode. The stuck in 1600 ISO occurs if the in-camera ISO is set to Auto. If I set the in-camera ISO to another setting, that setting takes precedence over any ISO setting made in Meteor.
I'm fine with that. As long as I can set the ISO and it works, regardless of how, I'm good.
Thanks for all the help Waterwingz, sorry to be such a PITA.