1990 Eagle Talon Slightly high idle at normal operating tem

Maybe unrelated but this "problem" started right after I left my lights on and drained the battery. I "jumped" the car and it started right away; battery charge came up quickly and has been fine since (3 weeks ago).

I am the original owner. The "hot" idle speed has always been around 650-700rpm until I drained the battery. It is now 1000-1100rpm but only gets there a few seconds after coming to a complete stop. If I take it out of gear, at any highway speed (5mph to 75mph), the rpm drops to about 1400rpm and stays there until I stop the car.

Having been an auto & aircraft mechanic (many years ago) I thought I would just adjust the mechanical idle screw to a lower idle rpm. That's when I discovered this engine has no mechanical idle adjustment (computers!).

So, what's your suggestion for getting the idle speed back to "normal"?

Thanks in advance for your help.

JLH