1999 Chevrolet Camaro V6 Misfire Code P0301B and EGR Issue P0404 - Diagnosis and Fixes

My 1999 Chevrolet Camaro V6 with automatic transmission has reached 70,000 miles and is showing two OBDII diagnostic trouble codes: P0301B (cylinder 1 misfire) and P0400 (EGR control circuit range/performance). The Service Engine Soon (SES) light flashes during cruise at around 70 mph and remains on, especially when accelerating from 2500 to 3000+ rpm. I notice a sluggish throttle response under these conditions. After cold soaking and restarting, the SES light stays on steadily but acceleration has improved. I cleared both codes and completed a drive cycle — the EGR code returned, but the misfire code did not appear during that test. However, I now observe sputtering when accelerating at half or three-quarter throttle between 1500 and 2700 rpm, with noticeably better power output above 3000 rpm (stock engine, no turbocharging). Additional observations: The fuel gauge appears inaccurate, sometimes showing a variation of up to one quarter tank. In cold weather (< freezing), I observe rapid voltage fluctuations between 13.5V and 15.0V; in warmer conditions, the voltage stabilizes at around 14.2–14.5V. I'm unsure if these electrical issues are related. Possible causes: Could a dirty or faulty EGR valve be causing cylinder 1 misfire? If so, would cleaning suffice or is replacement necessary? Would an EGR issue typically cause a single-cylinder misfire — or should it affect multiple cylinders randomly? I'm also considering spark plug and ignition wire issues, especially given GM's known poor placement of wires behind the engine. Are there other potential root causes I should investigate before replacing parts? Any insights or troubleshooting steps would be greatly appreciated. I want to avoid unnecessary repairs that don’t resolve the underlying issue. Thanks in advance for your help!