I have an N10 Y pipe with 2 bad CAT's in my shed. I was going to cut the pipes, core the CAT's some how. and find a quality welder to put it back together. But it'll never line up properly.
Now I'm thinking of putting a 2" cutter head on my RIDIG sewer machine, and just having a go at it. Just ream the **** out of it with a sewer machine. maybe even put a video camera down there.

I'm sure i'll be the 1st attempting this AI says illegal, stop here

 

Just get a new system without

 

They do NOT exist. N10 was rare.

 

Not sure about "rare"; maybe compared to other versions of these cars, butt not really "rare".

However all that may be, what's their physical shape? Length, flanges, any bends, etc.? If they're straight and of some reasonable size, how about cut either them or the pipes around them, and put in some slip-fit ones? Where are you? (as in, what regulatory restrictions, if any, do you face) How about get rid of the factory setup and put in an aftermarket single-cat system that flows better?