I have an instance of Maul on a stereo Aux track in Logic 9.1.8 64-bit; when I run a hard-panned signal into the Aux, I'm getting an equal amount of said signal in the middle at the output of Maul rather than it maintaining it's panning.
I was using it as an insert on an Aux track in Logic 9.1.8 64-bit, OSX 10.6.8, which was being fed by five tracks of saxophone. The saxes were panned hard L & R but post-Maul I was hearing lots of sax in the center. Switching out distortion processing to iZotope's Trash2 maintained the panning of the saxes as expected.
I'm happy to provide any additional info you need!
I installed 10.0.0.4 and it's still behaving the same. It seems to happen most obviously using the "Asym" model under "Overdrive". Moving a hard-panned signal even slightly towards the center seems to add a lot of signal in the center that sounds almost detached or delayed from the side signal. Conversely, using the "DCAM>Transistor" model maintains the panning as expected. Perhaps it's a side-effect of certain models and isn't a bug?