> Then most of the aftermarket ones
> have less material either in length of the core or diameter.

When I put an EJ25 in my Syncro, I also needed a new muffler and
cat.  They were original with 150,000 miles.  Next door to my
mechanic is a metal recycler.  We walked in with my cat and he
looked up in his book and handed me $65.  An aftermarket cat
was worth $0.

Wonder what my stock dog is worth?  ;-)

Richard