codes 361 and 321

[Alpha One]

My 94 LeSabre once every week, or every two weeks, stalls. After 10 or 15
minutes it starts again and works normaly until the next time. At the time
it guives the engine codes 361 and 321, but when working normal has no codes present. I don't think is the ECM because I substituted it with another from my other buick and it did the same think.
Anyone know anything about this?

Thank you