Black soot in tail pipes

[surfbeast]

The IAC is the part that is on the upper plenum toward the front of the engine. The black hose with the black box that runs from the intake tube connects into it. It looks like a small cylinder , a connector plugs into it and the unit is bolted into the upper plenum. If the car is running and you remove the black hose from the IAC the car dies. You can unbolt the IAC and remove it from the plenum, squirt some cleaner into it and let it dry. Put it back on and see if that helps. Hope this works and isn't to confussing.
You could also try cleaning the MAF sensor.

IAC = Idel Air Control