96 Buick LeSabre Stalling. S.O.S.
 

We bought a '96 Buick LeSabre a couple weeks back and have only ran into problems. We replaced the heater core and thermostat because of an unrelated issue and we have also had the Serpentine Belt pop off once, and we put that back on (both I believe, are unrelated) after we replaced the Heater Core, we started having problems stalling at red lights and once or twice, while driving, always going less than 40mph when it happens. Would only happen maybe once a day or so, and would start right back up every time. We cleaned the Mass Air Flow Sensor and it drove like a dream for 2-3 days and then stalled at a red light again. We replaced a vacuum hose that was attatched via electrical tape which was causing the car to go into low idle and ever since then it's gotten worse. It stalled maybe 5 or 6 times in one day and we would have to wait sometimes 25 minutes for it to start again. The car wasn't able to make it more than a few blocks and then finally, after the last stall, it refused to start back up completely. We went back to it the next morning and it started fine. Bought a new Mass Air Flow Sensor and replaced that. Found that the bottom of the old one was broken off and a piece was stuck and we had to fish it out. We figured, that HAD to be it. She ran fine for about an hour after and then stalled again while idle. We have no idea where to look now. Please help.