Im not sure what is going on but when I slow down or even rev the engine a little, the rpms fall pretty slow. Sometimes my foot will be on the brake at a red light and the rpms will just be getting down to idle rpm...
Is this my IAC? I just cleaned that thing not too long ago....
You also need to see what the stop screw is set at on the top of the top of the throttle body. Tighten it all the way until it stops, then back it off 1 and 1/2 turns exactly. That should cure it.
If your idle speed drops too low after that adjustment, use the throttle stop screw on the side of the TB to adjust base idle speed. But I would replace the screw with a hex headed screw while you are there, which will make idle adjustments a piece of cake in the future.
Scott