1996 Windstar 3.8L Split Port with P0300: Random Misfire After Warm-Up in Temperatures Above 45°F

I own a 1996 Windstar with a 3.8L split-port engine and automatic transmission. After driving for 30 minutes or more and then parking for approximately 15 minutes, if the ambient temperature is 45°F or higher, I experience random or multiple misfires accompanied by a flashing check engine light (code P0300). The issue typically resolves after running the vehicle for about two minutes—after which the check engine light stays on but the engine runs smoothly and performs well during acceleration. Cold starts are generally fine when temperatures drop below 45°F, even after a 30-minute drive and 15-minute parking period. After several driving cycles, the check engine light eventually turns off. I've replaced the spark plugs and plug wires (both showing 45,000 miles), changed the fuel filter, used Lucas injector cleaner, and replaced the coil pack. No visible arcing is observed in the plug wires. Despite these efforts, the P030 or misfire issue persists under warm conditions. Any insights or suggestions for diagnosing this specific behavior? Is it likely a sensor issue, fuel delivery problem, or something else related to engine temperature and idle stability?