So I just installed a DP on the F55 (universal high flow cat will be installed in a few days). I'm getting a heavy exhaust smell and I think it's coming from the engine bay and through interior vents. What could I have messed up? or does it just smell so bad that it seems like like it's coming from the engine bay?

 

Mine is noticeable but not over powering. Maybe your ring around the DP and turbo is not making a good connection.

 

The clamp holding the dp to the exhaust side of the turbo could be sitting incorrectly causing a small leak. It happened to mine the very first time I installed the downpipe