Mercedes P0130 P0150

Hi,
first of all, help! I'm having a problem with these two codes, P0130 and P0150, on a 1996 Mercedes E320 Elegance.
I've already replaced the O2 sensors, checked for exhaust leaks, air intakes, and other issues. Any suggestions would be greatly appreciated.

According to the manual, these codes are from sensors on one of the two banks of the engine. They appear because the sensors maintain a reading of 0.4 to 0.6V for more than 15 seconds. If both sensors are showing a fault, the engine is malfunctioning, possibly due to a very lean fuel mixture. You can check the live data with a scanner. The sensors can generate readings as low as 0.9V or, at one extreme, 1.2V if the fuel mixture is too rich, and this reading only increases significantly when accelerating abruptly. At idle, the readings almost always fluctuate constantly, and if the sensors don't fluctuate much or remain static, this type of problem can occur. Tell us how these sensors fluctuate so we can help you. If your vehicle has a mass airflow sensor, try cleaning it or replacing it to see how the oxygen sensors react


Here's a screenshot of the repair procedure for these codes