Stalling Corsica

1993 Corsica, 3.1L, 260,000 kms. Has recently had full tune up;new plugs, wires, all filters changed, etc. Also new catalytic converter installed. Problem is car stalls sometimes when slowing down from highway speed to make a left turn(never on right turns)car starts shaking and shuddering, prelude to stalling. After it stalls there is always a strong smell of sulfur. Could it be something as simple as a plugged or partially plugged EGR valve?Fuel, air, pcv valve replaced within last month. Oil changes are always done on time as well. Has me scratching my head, trying to figure out what the heck is wrong.