I did some searching and couldn't find anything like my issue, apologies if I missed something.
Ok; truck is a Bronco II crawler with a Ford 351M, mild cam, nothing crazy, swapped a GM TBI onto it with a 1227747, running a Moates Ostrich and TunerPro.
Got VE, AE, PE etc sorted and it works really well except for one issue I admit I can't figure out - any (most) of the time it's been in gear (automatic) and I shift it into park, the idle hangs around 1100 RPM.
No VSS in it, tried MPH to idle in my tune from 0 to 4 with no difference
Park sense switch which I can monitor in scanner data and it shows P in park.
TPS voltage is 0.90 at idle - I've set TPS voltage for idle to 0.94 in my tune thinking the ECM assumes idle at anything under that value
I've set idle speed in closed loop to 800 - as long as I leave it in park, or don't leave it in gear too long, it will maintain that RPM.
I've set IAC vs Temp to 1 in the entire table
Stall Saver isn't occuring (in at 500 and out at 650)
Retract IAC for voltage drop isn't the issue (scanner data shows ECM voltage above my setpoint in the tune at all times)
The IAC counts at idle before I pull it into gear are around 20 (RPM at 800) - once It's been sitting in gear for a long enough period of time that the IAC has to compensate to maintain 800 and I put it back in park, the IAC shows approx 70 and the RPM remains at about 1100, and it stays there until I shut it off - so the ECM is commanding this high idle speed. If I shut it down and immediately restart, it will get back into CL pretty quickly (I installed a heated 4 wire O2 from a later model GM to help keep it in CL on the trails) and the idle stabilizes at 800 RPM.
It seems as if once the ECM raises the IAC count to maintain the desired CL idle speed in gear it can't bring it back down for some reason once put back in park.
I admit to not knowing how to data log as I'm using a scanner that does that on it's own so I can't post a log...
If anyone has any thoughts or suggestions, or needs more info, please let me know.

Thanks in advance - D