Overactive ABS during a slow stop is usually a sign of a wheel speed sensor dropping out. I have had tremendous luck following the TSB on this problem for GM's. Basically they want you to pull the front sensors, clean rust build up from the mounting area, apply di-electric to the area and reinstall the sensor.
The sensors on the front are held in with an allen head bolt I think. If the bolts break free your halfway there. Gently work out the sensor and your home free. It won't cost you anything to give it a try. It is a lot easier to narrow down the sensor with a scan tool. Cleaning the fronts would be a good start.