My 93 245 is having a hot weather runnability problem.

Last summer I had some similar troubles -- the car would lose power and die after 20-30 minutes of city driving when the air temp was above 85-90 F. I would crank the heater in an attempt to stave off the stall.
After resting 10 minutes or so it would start again, sometimes with low power. The more cool-off time, the better it ran. Popping the hood helped with the recovery time. The temp gauge always read high when this was happening.
So I pulled the radiator and backflushed the fins with a garden hose to improve airflow. Also flushed the coolant side and replaced coolant. No more problems in 2006.

Fast forward to Friday the 14th...
Another hot day in St. Paul and the car stalled on me again. Waited a few minutes to restart and made it home on low-power with a couple more short stalls along the way. Temp gauge did not read high (I guess the backflush did something!).

So, I came back to the BB for new ideas. It sounds like this could be:
1. A bad coil that is failing when it gets too hot. Resistances check out just fine when the engine is cold / warm.
2. A bad crankshaft position sensor that is failing when it gets too hot.
3. Any of 100 other elements of the ignition and fuel delivery system.

Thoughts????