My car starts and drives great until it's fully heated up then is stalls (even when driving at normal speeds (30 - 60 mph). After it stalls it will not start up again, but will crank over just fine. After waiting about an hour or so the car will start up again, but stalls after warming up. I have a 1989 Mazda MX-6 (standard transmission) with 93K miles on it, and the car is in mint shape besides this recent problem. What could the problem be - something related to fuel delivery?

Optional Information:
1989 Mazda MX-6 4 cyl

Already Tried:
new spark plugs, new cap and rotor, fuel injector cleaner