2005 GMC Express 3500 Vortec 6.0L V8: P0300 at Idle and P0308 at 2500 RPM - Injector 8 Ticking Noise

Good morning, I own a 2005 GMC Express Cutaway with the Vortec 6.0L V8 engine. I purchased it with the check engine light on and multiple ignition-related fault codes. After inspecting, I found the ignition components to be quite old, so I replaced the spark plugs, wires, coil packs, air filter, and oxygen sensors. Despite these repairs, I'm now left with two distinct trouble codes: - P0300: Random misfire detected at idle - P0308: Cylinder 8 misfire detected when RPM is increased to approximately 2500 This pattern has been consistently verified multiple times. I've noticed a clear ticking noise coming from Injector 8, which strongly suggests it's the source of the misfire. I attempted to clean the injectors by spraying nearly an entire can of carb cleaner directly into the fuel rail (the van ran off for about 10 minutes). I also cleaned the throttle body and plate using carb cleaner while the MAF sensor was disconnected. During this process, no fault codes appeared on the scan tool. The vehicle starts reliably every time, idle is stable, and overall drive performance seems normal. The MAP sensor tests (voltage and frequency) appear to be within specifications, and the MAF reading at idle is around 6 grams per second. I'm now out of conventional troubleshooting options. Should I consider a failing injector or potential fuel delivery issues? Any advice on next steps would be greatly appreciated.