If you are setting the idle target base all the way to zero and the car is still idling at 3000rpm's, then the AEM isn't your problem. There is a mechanical reason for it.
I've seen IAC valves hang before; especially if you take it apart to clean it. I'd also check your TPS in the tuning screen... Does it read 0% at idle with your foot off the gauges? TPS sensor could be bad, or the harness isn't plugged into it.
Is your throttle blade fully closing? Something could be causing an obstruction. I'm thinking obvious things to look for here since you think there isn't a boost leak. I don't think so either, it would have to be a big obvious leak for that to occur. Is your IAC making a hissing noise by chance?
One thing you can try - Remove your IAC from the intake manifold, fully extend it so that it's at the position base 1 (lowest idle rate), re-install it, but DO NOT PLUG IT BACK IN. If your idle is extremely low, then the IAC valve is the problem.
Again to clarify, you need to rotate it so that it's extended all the way out, not all the way in. All the way out gives the lowest idle position, all the way gives the highest idle position.
And remember, DONT PLUG IT BACK IN. If you plug it back in, the ecu will move the idle stepper; you want to test it at the 1st position to see if it lowers idle or not.
Let me know how that works out and report back.
- Hams