Fit your M278 CLS550 Biturbo with the best dry air filters you you can get.  The AFE Magnum Flow air filters will increase power and reduce fuel consumption ( if you can keep your foot of the gas). These are Dry filters, so there is no messy oil needed that can cause problems with yoru engine. This is a great standalone mod for your M278 CLS550 Biturbo or a highly modified one.  When these filters get dirty , simply wash them, let them dry and reuse.