Is it normal for air to blow out of the catalytic converter's pipe (for the split air pipe) if there's no split air pipe hooked up to it?

I was wondering if that would cause an exhaust leak (it wasn't very hot though).

I don't get where it could come besides from the exhaust (unless the cat puts out gas on it's own?).

And can I cap it off if it's not normal?

 

hook the tube back up, or suffer a blown cat and exhaust possibly coming into the cabin.

 

That is the Pressure for the Aux ports ..So ya,it is normal,and Yes it would BE an Exhaust leak.if you plug it,Assuming you have an S4,you are either going to have to find another way to Open them Or Wire them open.

 

yeah there exhaust escaping out the tube instead of pushing the aux ports apparently causes premature cat failure . . .

 

...well, it's an S5, so that's kind of irrelevant.

What I wanted to know is if it's normal to have air coming out of a catalytic converter, and whether it causes an exhaust leak.

 

yeah its a leak

 

Its a hole coming out of your exhaust system. Thats seems like the definition of an exhaust leak to me. Also, it functions the same way on an s4 and s5, its just that the s5 doesnt have the extra thing going to the aux ports.