I figured this out after a friend suggested I export as an OBJ in Maya and re-import in Maya to fix funky normals. If you use Spin Faces a lot and merge vertex sometimes you can end up with geometry that will not tolerate smoothed normals properly. Problem can't be fixed with set to face, delete history, cleanup, or anything else. I found that if you do a quick "Polygons>Cleanup" then export your model as an OBJ, import into Zbrush, then immediately just export it back from zbrush as an OBJ - Zbrush fixes all the normal problems. I guess the program has a really low tolerance for poor or crappy normal information, anyway I don't know if this is a solution to anyone's problems YET. But this discovery has been huge for me, Yay ZBRUSH! This really helps when you try to duplicate faces of a mesh and combine/merge them back to the original mesh and normal problems emerge.