2006 Jetta TDI 1.9L BRM Engine Issues: P0101, P0102, and P2196 with Black Smoke and Poor Fuel Economy

Hi there, I own a 2006 Volkswagen Jetta TDI equipped with a 1.9-liter diesel engine (BRM variant). The check engine light is currently on, and the onboard diagnostic system has logged three trouble codes: P0101, P0102, and P2196. Codes P0101 and P0102 relate to the Mass Air Flow (MAF) sensor, while P2190 indicates an issue with the oxygen sensor — specifically, a lean fuel condition or misfire that leads to excessive black smoke during acceleration and rough engine performance. I recently replaced the MAF sensor and cleared the codes. However, after approximately 20 miles, the check engine light returned, and the same codes reappeared. The vehicle still exhibits heavy black smoke on acceleration and runs roughly. Fuel efficiency has dropped by about 10 mpg compared to previous usage. I have not yet replaced the oxygen sensor because I want to ensure that any part replacement addresses the root cause rather than just masking symptoms. I'm seeking advice from experienced users or mechanics — is there a possibility of deeper issues such as fuel injection problems, engine timing, or intake system leaks? Could the MAF sensor be faulty despite being replaced? Or could the oxygen sensor issue be related to a larger system malfunction like a clogged diesel filter or poor fuel quality? Any insights or diagnostic suggestions would be greatly appreciated.