"I don't really mean to be a downer here, but if you had pulled *me* over and given me a "stern talking to" about the fact that my car was *dirty*, I would likely have wound up getting arrested for punching your lights out right then…"
As it turned out you need a T12 socket for removing the exhaust from the catalytic converter. The T10 socket is needed to remove the bolts from the catalytic converter heat shield except there is not enough clearance for the socket and the wrench. I was able to remove them with an 8mm open end wrench. If you are daring and don't mind removing other components to get better access it might work with the T10 socket but I did not want to complicate this by taking other components off and have to put them on. I guess I was being lazy.