I am currently having a similar problem with our newly installed Roe SC car. I originally thought the IAC was bad, but replaced the battery instead on advice from JD---At 55,000 miles and over 6 years old....it was due. (the old one still load tests OK) That fixed the problem temporarily. My problem is slightly different in that I have set 3 PO153 codes and 1 PO174 code over 2400 miles. There's 100 track miles in there as well---the car ran great! The symptoms seem exactly the same though....wanting to stall when decelerating to a stop....going low and sometimes stalling, sometimes it will come back on it's own. A slight throttle blip coming to a stop and she's idling normally. Resetting the computer fixes the problem until a light sets again. I erased all the lights with my little OBDII reader/eraser, but I guess that won't reset the adaptives.
I have replaced the left front O2 sensor with no luck. Sean thinks it's in the adaptives and that the reason is a bad voltage signal to the PCM from the left side. He told me to add 20ms to 1,3,5,7,9 and try it again. If adding fuel like this twice does fix it, i'm going to buy an OEM O2 sensor for the left (I bought Bosch for the replacements).
You could try disconnecting all 3 PCM plugs to reset the adaptives. Then show the TPS full throttle voltage and see what happens.
Steve