I am not sure if the make and model of the car is important. The initial code indicated both banks running lean at load. I instructed to check for the vacuum leak and then clean MAF. Afterwards, fuel trim is indicating that it is running excessively rich on both banks. Is it possible that too much cleaner on the MAF can make it give false rich readings to computer? A modern fuel injected car would suddenly start running rich on both banks only if the fuel pressure regulator malfunctions. Other causes such as exhaust leak before O2 sensor can be ruled out because it is unlikely that similar leak would develop on both banks simultaneously. O2 readings on the scanner indicate that both O2 are functioning correctly. Air cleaner element is NOT clogged With MAF disconnected short term remains pretty much in neutral territory and car run reasonably well. So changing MAF is already planned for. But most MAF when they go bad, the engine starts running lean and not rich. OEM MAF is $$$$ for this "mistress" so first attempt would be made with a ebay MAF as it costs 10% of the OEM money. Of course, if that does not fix it, we would have to decide if we need to shell the big money for the OEM one or to approach different diagnostic strategy. Any suggestions?