[Overdrive]

^^ A good point. Another place to check for a sneaky vacuum leak is the filler neck for the engine oil that runs down from the area where the oil cap is in the trunk. If it is cracked somewhere though, it'll need to be replaced.

I was also wondering about fuel, but not thinking that's too likely a culprit because you're running fine until it gets hot.

Question though: When the car stalls as you come to a stop, how does it act on restart? Is it hard to start back up? Does it run fine for a bit before acting up again? Does it immediately start running poorly again?

Like jsceash pointed to, though, you're probably looking at a vacuum leak somewhere, and sometimes they're in really stupid and/or annoying spots you wouldn't even suspect. If you're still not having any success after the checks he mentioned, maybe take a look at the heads to see if the gaskets are leaking.