1994 Buick Lesabre ignition module

Usually after some driving (one or two hours) my 1994 Buick Lesabre will cut out intermittently as if gas was not getting to the engine. One time it stalled on the highway but when I got back into it an hour later it started easily and ran fine for months afterward. Had the fuel pump tested last year when the problem started and it was 40PSI (specs are 41-47PSI). Replaced the inline fuel filter (twice) and the air filter several times (cheap solutions to a problem but didn't make a difference). My mechanic told me to get an ignition module from a wrecker which I did and installed. But the problem persists. It's hard to eliminate the ignition module as a possibility because it was a used part and the problem is occuring when the engine is hot. It seems to me a fuel pump would act up any time and frequently. I've noticed that this problem doesn't occur when the weather is cold. Any ideas out there would be appreciated. Thanks.