Its probably your fast idle thermo valve.
You can test it...pull off the intake, cover the lower left hole on the inside of the TB while the car is idling funny...if the motor sputters down to a low idle and stops surging, its the FITV.
It is located on the bottom of your TB. 3 10mm screws. Remove it, cover the top part in duct tape/vinyl (something that wont melt) and pop it back on. I bet your idle goes back to normal.
Is the idle stable once the car warms up?