Did you find a solution for the high idle slow rpm drop on your 2.3-16? Did you fix the problem by replacing your ECM?

I'm having the same issue with my 86. It certainly makes shifting and stoplights exciting.

NOTE: I've found that if you quickly turn the key back (off) one position to shut off the engine and then quickly turn it back (on) to the run position the idle comes back to 800-900rpm .....but this is only a temporary fix until the throttle position changes and it's back up to 2500 rpm.