Gilly, those washable knn air filters require spray of oil around it after you wash it.. I think that oil is causing the MAF's sensitive wire to be dirty and covered, also I believe the knn air filters don't do a good job in filtering the dirty air.. so more dirt and pollution goes through the air mass sensor compared to the oem paper filter.. Never use knn air filters or cold intake on a ML, cuz it'll cost you $500 to replace the air mass for something that doesn't really speed up your car..