TBI with High Idle in PARK

[JJK10]

700 seems high for base idle to me. I aim for around 500-550 when I set that, Should be lower than target idle, not higher. If it’s higher, ECM will be trying to lower rpm with the IAC, but it can’t. And I think you can actually damage the IAC that way. But I might be misreading your post on this....
With the ODB1 jumped and the IAC forced closed I set the idle on the throttle blades at about 525..

Another thing to look at in the tune... there’s a setting for IAC differential between neutral/park and drive. Perhaps that is set wrong, i.e. it doesn’t drop it enough when you go to park.

You could be on to something! but I have no ability to check that... Thanks much for the input!