2001 Duramax Diesel Misfire on Cylinder 6: Diagnosing No Smoke, Codes 0306, 0380, 0004, and 4800

I'm experiencing multiple diagnostic codes on my 2001 Duramax 2500 HD with Allison transmission, crew cab, 4x4. The codes displayed are 0306 (Cylinder 6 misfire), 0380 (fuel system issue), 0004 (fuel pressure low), and 4800 (cylinder misfire). The engine exhibits a noticeable miss at idle, but there is no visible smoke—only light black exhaust when under load. I have extensive experience working with diesel engines and have never observed an industrial diesel engine failing to change exhaust color during a misfire, whether at idle or high RPM. This absence of smoke makes me skeptical about a failed cylinder being the root cause. I've read extensively about potential electronic faults in the injection system and limitations of generic OBD-II scanners for accurate diagnostics. I allowed my wife to drive the truck regularly around the ranch and during horse feed hauling, initially attributing the issue to heavy use. However, even after she returned from racing, the problem persisted without improvement. The truck has 160,000 miles on it. Chevrolet previously replaced the injector pump at 95,000 miles and all injectors at 145,000 miles due to a high fuel flow code. Since then, I've parked the vehicle to prevent further damage if a cylinder failure were present. Given that there is no smoke, I find it highly unlikely that a single cylinder is completely failed. Many online discussions point toward wiring issues such as wire chaffing or poor connections—yet upon engine disassembly, I found more wires than a typical residential home. My question: where should I begin troubleshooting potential wiring faults? Should I invest time in diagnosing myself, or is it better to return to the dealership for professional service? I don't know of any qualified independent mechanics in this area, so dealer support remains my only option. Any insights or suggestions on how to proceed would be greatly appreciated. If additional details are needed, I'm happy to provide them. Thanks!