2007 Mercedes E320 Bluetec Diesel P0101 Code: Diagnosis and Solutions

I own a 2007 Mercedes E320 Bluetec diesel sedan with 135,000 miles. The check engine light is on, and I've retrieved two identical fault codes: P0101 (Mass Airflow Sensor Range/Performance Problem). Steps taken so far: - Replaced both air filters - Verified airflow to the filters; no obstructions found - Removed the center Y-tube MAF housing (this model has dual MAF sensors), removed and cleaned both MAF sensors using CRC MAF cleaner, and cleaned the mesh inside the Y-tube assembly - After disconnecting both MAF sensors temporarily, the car initially shifted better and felt more responsive. However, after turning it off and letting it sit for 15 minutes, it entered a 30–40 mph LIMP mode upon restart. - Inspected all electrical connectors to the MAF and Y-tube assembly — all appear secure and undamaged Each time I perform a fix, the code clears temporarily but returns shortly after. I am hesitant to invest $225+ in new MAF sensors from Germany, as they are not sold separately in the U.S., and the full assembly costs between $450–$500. The only remaining step I haven't completed is disconnecting the turbocharger line to the intercooler to check for potential leaks or restrictions that could affect airflow sensing. Any insights, especially regarding P0101 in Bluetec E320 models, would be greatly appreciated. I need to register this vehicle soon and am looking for a cost-effective, reliable solution.