When it dies, will it start right up clean or does it misbehave a bit on start up. Start up clean it probably was lean. Misbehaves and it is having to burn the raw fuel off the plugs. I REALLY like running an AFR gauge in a car. When the car has an issue. The gauge will quickly reduce the number of possible causes. For example, if you looked and it was lean when it died, fuel supply and it removes ignition from the equation. Rich? Unless you have fuel dripping out of a booster or HUGE jets, (which can be pretty easy to see or test) it will probably be ignition.
