Stalling in Buick Riveria

Hi all I have a 95 buick riveria with over 200,000 miles on it. Recently I have had a problem with the car stalling at lights. It doesn’t do it all the time, but occasionally. If I turn the key all the way off and back on the car will start right up. It was also stalling while I was driving and hesitating. The mechanic said the problem was the ignition module and I did change that. That got rid of the hesitation, and helped the stalling, but not completely. It’s when I come to a stop and it doesn’t happen all the time. I will ask the mechanic for the computer codes he saw but frankly I can’t afford another scan at 95 dollars. Anyone have any suggestions of what else it could be?

Let me also mention that it is a supercharged engine. Ladymarvn