Oldsmobile/Buick Repair: 94 Buick Century Stalls upon stopping on full tank., purge valve, vacuum leak

Question
Ok I've been feeling something wrong with the engine for a while. About a month ago it stalled out at a stop light with a full tank of gas. It started back up after i put it in drive and gave it some gas. It didn't give me any trouble for another two weeks. Then it happened again, again at a stop light. This time i noticed that if i started it up and let it idle it would be fine but if i put it in reverse or drive it would immediately stall out. After about 5 minutes messing with it I got it back on and it ran fine again. Again this was on a full tank. So i thought maybe it was bad gas from somewhere so this time i tried filling up at Chevron instead but again a day after i filled up it stalled out. This time i felt it coming because you can feel it start to quiver as you slow down so I managed to get it into a parking lot. This time it took about 10 minutes to get it back on, and i drove it straight back home and I don't want to take the darn thing anywhere because I don't have the resources to tow it. I have a friend who is a mechanic but he is confused as I am on this one. I replaced the fuel filter the first time this happened. It didn't help.
Like I said you can feel it begin to quiver when it slows down. It doesn't stall out until you come to a full stop, or at least it hasn't yet; though on an uphill it felt like it almost did until I pretty much floored it to get to the top of the hill. And like I said after you get it started back up it's fine and it always seems to happen a day or two after filling up the tank.

Answer
It is possible the vapor recovery canister is getting saturated with raw gas, and when the purge valve opens, it is flooding the engine.
A vacuum leak is another possibility, but the full-tank symptom sounds more like the other.
See if there is liquid fuel in the vacuum hose from the vapor canister to the purge valve or manifold.

Van