One thing I would check is your TPS. I had this same issue or very similar. Turned out it was the TPS. I'd do a base idle reset and it would be fine and then I'd drive it and come to a stop and it would be idling at 2000 rpm. It's not the IAC that is the problem it's something telling it to open. In my case it was the TPS, worn out where it mates up to the butterfly valve. When you do a base idle reset after, you set your throttle body with your IAC unplugged to your desired idle rpm while running. Then with key on engine off you check your TPS voltage. Should be at .98 volts. If it's not then adjust it to that voltage. Then you can shut key off, plug IAC back in. Disconnect battery for 15 mins and reconnect. Good to go.