Regen Mode on My 2015 GMC Duramax REALLY STINKS!

The Regen Mode on my 2015 GMC Duramax REALLY STINKS! The truck has a little over 20k miles and I have always noticed a diesel smell in the cab of the truck (mostly when at a stop light) when regen mode is running. I noticed smoke from under the hood at about 10k miles and I took it to the dealer to have a look. They claimed they induced regen mode, let it idle for 30 to 45 mins and could not replicate my problem. They tried to claim the smoke was coming from a label on the pipe that had not been removed.

I took it home and always notice a little smell when in regen mode but now that it is getting cold out for some reason I smell it really bad when stopped and the windows are up. To the point you almost feel sick if you do not open the window.

Another complaint I have is even when I put the A/C on recirculate it still seems to bring in fresh air (in my case smokey air) from my down pipe.

Tonight when I got home I decided had enough and could not take it any longer so I opened the hood and saw smoke again pretty consistent. I decided to look below in the fender-well to find the issue and make a video of it to prove to the dealer there is an issue. Sure enough it looks like a wet diesel area at the joint in the down pipe. It looks like I am off to the dealer again to see what excuse they make up this time.