Intermittent P0304 Code on 1998 Windstar 3.8L: Diagnosis and Solutions

1998 Ford Windstar, 3.8L V6 engine, 154,000 miles, automatic transmission. The check engine light activates shortly after clearing the stored codes and begins blinking at random intervals and speeds. During these blinking periods, the engine runs very roughly. After approximately two minutes, the warning light stops flashing and the engine returns to smooth operation until the next occurrence. This intermittent hesitation is causing significant frustration. I have already replaced the spark plugs, spark plug wires, fuel filter, and the first oxygen sensor. Despite these efforts, the issue persists. I am seeking expert advice on potential root causes for this intermittent P0304 code and rough idle behavior. Any insights or troubleshooting steps would be greatly appreciated.