2001 Lincoln Continental P0308 Code: Diagnosing Spark Plug and Injector Issues

I'm experiencing a persistent P0308 fault code on my 2001 Lincoln Continental. I attempted to isolate the issue by swapping components: I swapped cylinder #8 coil with #7, cylinder #8 spark plug with #2, and cylinder #8 injector with #6. After these swaps, the P0308 code reappeared, indicating that cylinder #8 is still the source of the problem. I performed a compression test on cylinder #8, which read between 140 and 147 psi—within normal range. No significant vacuum leaks were detected during inspection. I have already replaced the air intake temperature sensor, cleaned the MAF sensor, and even disconnected it temporarily to see if performance improved. The car runs normally under load and drive conditions, so I'm wondering whether a faulty MAF sensor could be causing or contributing to this issue. Given that the code persists despite component swaps and normal compression, what are the most likely causes? Could it be an injector circuit failure or a misfire due to ignition timing issues?