2003 Smart For Two Cabrio Misfire at 2000 RPM with P2019, P201B, P201D, P201F Codes After Engine Rebuild

Hello everyone, After a complete engine rebuild on my 2003 Smart For Two Cabrio Cabrio, I'm experiencing a misfire on cylinder 2 specifically when the engine reaches around 2000 RPM. The engine starts and runs smoothly at idle with no misses or rattles. However, when I hold the throttle to approximately 2000 RPM, the engine suddenly drops to running on only two cylinders, triggering the EML (Engine Malfunction Lamp) light. This issue repeats consistently—after turning off the engine and restarting, everything is fine until the revs are held at 2000 RPM again. The same behavior occurs during road testing under load. The ECU reports the following diagnostic trouble codes: - P2019 - P201B - P201D - P201F I have already replaced the spark coils, spark plugs, and fuel injectors—no improvement. The issue persists. Could this be related to the crankshaft position sensor? Prior to the rebuild, the vehicle was frequently stopped abruptly during rainy weather and restarted immediately, which may have affected engine components. Any insights or suggestions would be greatly appreciated. Thanks in advance! Regards, Enrico