If you were looking for a big orange FRAM filter-like part, that might be why it's hard to find. That got me too, until I got my hands on a manual.
Peek over the back of the intakes by the firewall as posted earlier.
It sits right side up and is black. It's smaller than a typical oil filter. Unscrew it and the filter element is inside.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car