1992 Buick Lesabre EGR?

Engine Performance problem
1992 Buick Lesabre 6 cyl Two Wheel Drive Automatic

The car sputters and stalls when it drives enough to warm up (anywhere from 2 to 10 miles) I've replaced fuel throttle pos. Sensor and and a number of other things relating to this. Could it be EGR and where is it located? This is my mother in laws car and has had the car towed home a couple of times when it stalled. After a couple of hours to cool it will start again, but will stall when driven several miles.