2001 VW Jetta P0300, P0301, P0302, P0303, P0304 Misfire Diagnosis and Fix

I'm currently troubleshooting a 2001 VW Jetta with a 1.8L turbo engine. The vehicle exhibits severe misfiring during cold starts—when shifting into reverse or drive, it stumbles significantly. Applying full throttle results in no acceleration and a strong misfire; however, after revving the engine several times while in park or neutral, the engine gradually stabilizes and runs smoothly once warmed up. The only fault codes detected are P0300 (random misfire), P0301, P0302, P0303, and P0304 (individual cylinder misfires). I've tested fuel pressure and found it at 35 psi at idle, rising to 40 psi under load—within acceptable range. Spark plugs have been re-gapped and inspected; intake vacuum tests show no leaks. The vehicle is equipped with individual ignition coils, all of which function properly. I’ve also removed the exhaust manifold pipe for inspection, ruling out backpressure issues. Timing marks are confirmed accurate. Additionally, I replaced the throttle position sensor (TPS), which includes an IAC valve. Despite these steps, the problem persists. I'm now seeking advice—has anyone encountered this exact issue on a 2001 VW Jetta? Are there known solutions or common causes for P0300-P0304 codes during cold starts? Any insights would be greatly appreciated.