2005 Ford F150 5.4L with P0012 and P0021: Oil Pressure Drops, Phaser Noise, and VCT Issues

I own a 2005 Ford F150 Lariat with the 5.4L V8 engine and over 175,000 miles. For years, I've experienced what I believed to be phaser-related noise—no loss of power, no check engine light (CEL), and consistent performance during long-distance drives. Last year, after developing a 45–55 mph hesitation and jerking during upshifts, I replaced the plugs and coil packs. That resolved the shifting issue and eliminated any prior concerns about engine misfires or performance drops. However, last week, while driving just one mile from home, my oil pressure dropped below 'L' (low), and the truck began to stutter. I pulled over immediately—no loud metal-on-metal noise, no CEL illuminated. After restarting, oil pressure returned to normal. I then noticed a rough idle when starting the vehicle in the morning, with oil pressure dropping to 'L' at idle after a few minutes. The engine runs smoother now than before, but I’ve recently received a persistent P0012 code (Variable Valve Timing - Intake Camshaft Position) that returns after a couple of starts. I tried swapping the VCT solenoids and cam position sensors to the opposite side—no change in the code or symptoms. The knock sound is only present when cold, goes away after driving one mile, and reappears on subsequent cold starts. Current readings: - Cold idle: 50 psi - Hot idle: 20 psi I’ve already had my mechanic drop the oil pan, check for sludge, and replaced the FRAM oil filter. The engine was cleaned thoroughly, and performance improved significantly—no hesitation or low oil pressure. Key questions: 1. Could residual sludge in the engine be causing abnormal oil pressure readings? Would this mimic a higher-viscosity oil effect? 2. Did the initial issue involve a timing jump due to lack of driving (only idling)? Is there a way to check for this without removing the front cover? 3. Should I suspect the oil pump or phaser assembly despite current smooth operation? I’m looking for advice on what to test next before considering engine disassembly. Any experience with 2005 F150 5.4L P0012/P0021 issues, especially in Georgia? I'm open to trade—custom paint or airbrushing work for labor. Check my Facebook page: EagleEye.artwork if interested.