I just ordered a catback exhaust for my 93 civic sedan that has a 2.25 inlet, and I was wondering if a header with a 2.1 outlet will fit. Does a catback system include the cat? Also, my civic has a b16A2 transplant if that helps yall understand my question. Will the bolts that hold on my cast manifold work on the new header? Thanx for the help.

 

No, it does not include the CAT.

 

A catback exhaust does not include a cat.

 

Hence why its called "cat-back"

 

Exactly The exhaust will go from the cat, back to the rear of the car.

 

and you will need a header 4 b16a2.