S/V/C Airflow direction through a catalytic converter

2001 S40; 235,000 miles

Does the airflow direction through a cat. make a difference?

I'm in the process of installing a new Bosal cat. and noticed that an arrow etched on the new cat. goes in the opposite direction of the airflow. I am assuming the arrow indicates airflow.

I'd contact Bosal directly, but they're closed on Saturdays and I'd like to get this repair done by Monday.

Thanks

It matters. The rear chamber is for NOX reduction.

Thanks.
Unfortunately, my weekend project has come to a halt.

I kind of figured that if they put an arrow on it, there was a reason - duh.

Regardless, as it turns out, the inlet flange will not fit the turbocharger flange either.
The turbo outlet flange has a collar(?) that fits into the cat. The replacement cat. inlet flange is not cut out to accept the collar.

Side note - went to set up a return to Rockauto and got rejected because I misunderstood one of their return questions (it's all automated). Can't change my response either. Emailed customer service and explained the situation. Hopefully they see what I did and that the part is defective. Certainly don't want to be out $175.

Rockauto got back to me an hour after I emailed customer support.
They asked a bunch of questions and for photos.

I responded and the return was approved within an hour.
It ships back Monday.

Oh yea, their return policy is 30-days from when it was shipped from their warehouse.
Today was the last day to submit a return request. Complete luck on my part.
I thought I had 90-days.