Are you sure it's just not leaking onto the pan and then off the back. I currently have the same problem and can't seem to track it down. You may want to re torque the bolts again, they seem to loosen a bit after reinstalling a new pan/gasket. You don't really want the over torque, that's pretty soft metal. It's taken a while, but my leak has miraculously just about stopped since I replaced the pan. I may be able to get rid of the driveway rug now.