1999 Mercedes C230K - CEL Error: Malfunction in Bank 1 (MAF or O2 Sensor Issue)

My 1999 Mercedes C230K was displaying a Check Engine Light (CEL) with fault codes indicating potential issues with the Mass Air Flow (MAF) sensor or the pre-catalyst oxygen (O2) sensor. I began troubleshooting at the air intake system and discovered that the air filter was not only dirty but also crimped, which could potentially allow dust and debris to enter the MAF sensor. After carefully replacing the air filter, I inspected all vacuum hoses for leaks or deterioration—no issues were found. I drove approximately 55 miles with the CEL still illuminated. Next, I removed the MAF sensor from its housing and applied about two-thirds of a can of CRC MAF cleaner directly to the sensor element (without touching any wiring). I also sprayed the MAF housing and the O2 sensor connector that interfaces with the MAF. After reassembling all components, I noticed immediate improvement: no hesitation or skipping when engaging the turbocharger. Following this, I made three short drives totaling 35 miles, after which the Check Engine Light turned off. The issue appears resolved without any major repairs.