2006 PT Cruiser P0303 Misfire Cylinder 3 - Persistent Code After Multiple Repairs

2006 PT Cruiser Touring 2.4L 4-cylinder (non-turbo) | 100,000 miles I'm experiencing a persistent P0303 misfire on cylinder 3 that continues despite extensive repairs. I've already replaced the coil pack, spark plugs, ignition wires, and fuel injectors. I've swapped out multiple sets of plugs and wires, checked fuel pressure, voltage to the coil, plug, and injector, and performed a full diagnostic check. More recently, I've replaced the cam position sensor, MAP sensor, ignition sensor, knock sensor, crankshaft position sensor, ECU, and PCV valve. The P0303 code still persists. The misfire is intermittent: it sometimes clears when the fuel level drops below 1/4 tank and returns after refilling. Other times, it remains active even at low fuel levels. I can visually observe engine shaking — not severe, but noticeable. The engine runs smoothly for about 5 minutes after a reset before the misfire begins. When under load (e.g., turning on the AC), the misfire occurs earlier and more noticeably. The fluctuation pattern is gradual: RPMs slowly drop from 800 to 750, then the engine drops to 500 and oscillates between 500–750 every 6 to 10 seconds. On highway driving, this issue is often undetectable due to smooth operation. Cylinder 3 is not completely dead — it receives fuel (wet plug when ignition is pulled and injectors are active) and produces spark (equal wear compared to other plugs; voltage readings from the coil confirm proper output). Swapping plugs or wires has no effect. There's no backfiring, no loud exhaust noise, and no visible smoke or smell. I'm at a loss as to what could be causing this. I've tried every common fix — now I'm considering taking it to the dealership for further diagnosis. Any insights? This is clearly beyond DIY troubleshooting. Thanks in advance.