Welcome to the club. I too recently had an exhaust leak on my 2011 F250. Took it to the dealer who did a "smoke" test and discovered that an exhaust gas pressure tube bracket had come loose. After retightening the bracket, I have not had anymore exhaust smell in the cab. Go get it checked out. I waited thinking that it could be the active regen, but it didn't go away. A couple of hours at the dealer and no more nasty smell.