Exhaust from the street view...

You can have all the aftertreatment you want, but some basic exhaust requirements remain the same.

The exhaust has to be able to flow,,,, this exhaust damage is actually very common, another note, the exhaust tis are specific to each manuafacturer and need to be in like new condition due to the way they disperse the heat. We are talking about temperatures in the 1700* area.