Exhaust manifold back pressure sensor tube

[Old Driver]

Had a brand new exhaust manifold installed a few weeks ago since the section with the tube had no threads left. Cummins updated the exhaust manifold so i had a shop put in a complete new set. My one little problem im having is that ive got a very loud audible leak anything over 10psi coming from the slip joints on the new manifold. Everything was bew but this suckers leaks too much in my opinion. Ive talked to the shop that did the work and cummins has told them that i need to run it for a few months or about 50,000 miles so the joints will seal with soot over time. Ive got no other leaks anywhere in the charge or exhaust systems.
Is this normal for these things to leak right away? The manual says in the first paragraph that there should be no leaks. Im not sure if i need to get someone else to look at it or is cummins telling the truth?

https://youtu.be/PFbRY1P44U4