Audi TDI AEL exhaust manifold cracked - consequences?

Hi, I changed the diesel filter yesterday, and then when I tried to start the engine to fill it up, I noticed that it's smoking from somewhere in the front.
While inspecting, I discovered the cracked exhaust pipe. The crack goes all the way around, and when starting the engine, the turbo moves up to the crack, and the smoke escapes from there. When the engine is running, there is no abnormal noise, and when the engine is idling, no exhaust gases escape. It's clearly visible in the photo.
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Could this crack be causing poor performance in the upper area? I think so?
What further impacts could the crack have?

Thank you for the information.

It will be welded soon, but I didn't manage to do it this weekend.

Cheers.
Thomas.http://www.freitachnacht.de/Hosenrohr_Riss1.jpg{MARKER}

The crack certainly has no impact on the performance. It's too small for that.
Possibly, the cat is lost. This would become noticeable at high speeds.
He would likely whistle loudly from the crack under full load.

Based on how the crack looks, it should be possible to weld it.
When you're taking apart the catalytic converter, check to see if it's clogged.