For Export A:M-Models it is very important to check and change the Hooks and 5Pointpatches. Sometimes when make the Hooks and 5pp's the normals direction not corect. (You should change/check the normals everytime direct after create these patches)
Some other Application like C4D R9 or Lightwave can create NGones (feature like Hooks or 5pp's). For this app's, it is better when the 5PointPatches are holes, when exporting.
Steffen Gross had written a fantastic Plugin to select the Hook and/or 5pp's.
You found it here:
http://www.sgross.com/plugins/
He is a great A:M-Developer :-)